diff --git a/core/includes/ajax.inc b/core/includes/ajax.inc
index 026d630..7636d18 100644
--- a/core/includes/ajax.inc
+++ b/core/includes/ajax.inc
@@ -411,7 +411,7 @@ function ajax_base_page_theme() {
     // to see the default theme, token validation isn't required for that, and
     // bypassing it allows most use-cases to work even when accessed from the
     // page cache.
-    if ($theme === variable_get('theme_default', 'stark') || drupal_valid_token($token, $theme)) {
+    if ($theme === config('system.theme')->get('default') || drupal_valid_token($token, $theme)) {
       return $theme;
     }
   }
diff --git a/core/includes/config.inc b/core/includes/config.inc
index c143dd4..5b1fe21 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -12,22 +12,24 @@ use Drupal\Core\Config\StorageInterface;
  */
 
 /**
- * Installs the default configuration of a given module.
+ * Installs the default configuration of a given extension.
  *
- * @param
- *   The name of the module we are installing.
+ * @param string $type
+ *   The extension type; e.g., 'module' or 'theme'.
+ * @param string $name
+ *   The name of the module or theme to install default configuration for.
  *
  * @todo Make this acknowledge other storage engines rather than having
  *   SQL be hardcoded.
  */
-function config_install_default_config($module) {
-  $module_config_dir = drupal_get_path('module', $module) . '/config';
-  if (is_dir($module_config_dir)) {
-    $source_storage = new FileStorage(array('directory' => $module_config_dir));
+function config_install_default_config($type, $name) {
+  $config_dir = drupal_get_path($type, $name) . '/config';
+  if (is_dir($config_dir)) {
+    $source_storage = new FileStorage(array('directory' => $config_dir));
     $target_storage = new DatabaseStorage();
     $null_storage = new NullStorage();
 
-    // Upon module installation, only new config objects need to be created.
+    // Upon installation, only new config objects need to be created.
     // config_sync_get_changes() would potentially perform a diff of hundreds or
     // even thousands of config objects that happen to be contained in the
     // active store. We leverage the NullStorage to avoid that needless
diff --git a/core/includes/install.inc b/core/includes/install.inc
index 91e10a1..c3c91d8 100644
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -387,7 +387,7 @@ function drupal_install_system() {
   system_rebuild_module_data();
   system_rebuild_theme_data();
 
-  config_install_default_config('system');
+  config_install_default_config('module', 'system');
 
   module_invoke('system', 'install');
 }
diff --git a/core/includes/module.inc b/core/includes/module.inc
index 0f0f705..ab45576 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -462,7 +462,7 @@ function module_enable($module_list, $enable_dependencies = TRUE) {
         $version = $versions ? max($versions) : SCHEMA_INSTALLED;
 
         // Install default configuration of the module.
-        config_install_default_config($module);
+        config_install_default_config('module', $module);
 
         // If the module has no current updates, but has some that were
         // previously removed, set the version to the value of
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index d75fbd7..bb51946 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -9,6 +9,7 @@
  */
 
 use Drupal\Core\Utility\ThemeRegistry;
+use Drupal\Component\Utility\NestedArray;
 
 /**
  * @defgroup content_flags Content markers
@@ -62,7 +63,7 @@ function drupal_theme_access($theme) {
  * @see drupal_theme_access()
  */
 function _drupal_theme_access($theme) {
-  $admin_theme = variable_get('admin_theme');
+  $admin_theme = config('system.theme')->get('admin');
   return !empty($theme->status) || ($admin_theme && $theme->name == $admin_theme);
 }
 
@@ -82,7 +83,7 @@ function drupal_theme_initialize() {
 
   // Only select the user selected theme if it is available in the
   // list of themes that can be accessed.
-  $theme = !empty($user->theme) && drupal_theme_access($user->theme) ? $user->theme : variable_get('theme_default', 'stark');
+  $theme = !empty($user->theme) && drupal_theme_access($user->theme) ? $user->theme : config('system.theme')->get('default');
 
   // Allow modules to override the theme. Validation has already been performed
   // inside menu_get_custom_theme(), so we do not need to check it again here.
@@ -659,7 +660,7 @@ function _theme_build_registry($theme, $base_theme, $theme_engine) {
  *     their base theme), direct sub-themes of sub-themes, etc. The keys are
  *     the themes' machine names, and the values are the themes' human-readable
  *     names. This element is not set if there are no themes on the system that
- *     declare this theme as their base theme. 
+ *     declare this theme as their base theme.
 */
 function list_themes($refresh = FALSE) {
   $list = &drupal_static(__FUNCTION__, array());
@@ -1287,6 +1288,7 @@ function drupal_find_theme_templates($cache, $extension, $path) {
  * @return
  *   The value of the requested setting, NULL if the setting does not exist.
  */
+
 function theme_get_setting($setting_name, $theme = NULL) {
   $cache = &drupal_static(__FUNCTION__, array());
 
@@ -1296,23 +1298,31 @@ function theme_get_setting($setting_name, $theme = NULL) {
   }
 
   if (empty($cache[$theme])) {
-    // Set the default values for each global setting.
-    // To add new global settings, add their default values below, and then
-    // add form elements to system_theme_settings() in system.admin.inc.
-    $cache[$theme] = array(
-      'default_logo'                     =>  1,
-      'logo_path'                        =>  '',
-      'default_favicon'                  =>  1,
-      'favicon_path'                     =>  '',
-      // Use the IANA-registered MIME type for ICO files as default.
-      'favicon_mimetype'                 =>  'image/vnd.microsoft.icon',
+    // Provide defaults as function is used before config installed.
+    $default_config = array(
+      'favicon'  => array(
+        'path' => '',
+        // Use the IANA-registered MIME type for ICO files as default.
+        'mimetype' => 'image/vnd.microsoft.icon',
+        'use_default' => 1,
+      ),
+      'features' => array(),
+      'logo'     => array(
+        'path' => '',
+        'use_default' => 1,
+      ),
     );
     // Turn on all default features.
     $features = _system_default_theme_features();
     foreach ($features as $feature) {
-      $cache[$theme]['toggle_' . $feature] = 1;
+      $default_config['features'][$feature] = 1;
     }
 
+    // Cache a config object that will merge $default_config,
+    // system.theme configuration and the theme's config.
+    $cache[$theme] = config('cache.' . $theme);
+    $cache[$theme]->setData($default_config);
+
     // Get the values for the theme-specific settings from the .info files of
     // the theme and all its base themes.
     if ($theme) {
@@ -1329,59 +1339,107 @@ function theme_get_setting($setting_name, $theme = NULL) {
       }
       foreach ($theme_keys as $theme_key) {
         if (!empty($themes[$theme_key]->info['settings'])) {
-          $cache[$theme] = array_merge($cache[$theme], $themes[$theme_key]->info['settings']);
+          $cache[$theme]->setData(NestedArray::mergeDeep($cache[$theme]->get(), $themes[$theme_key]->info['settings']));
         }
       }
     }
 
     // Get the saved global settings from the database.
-    $cache[$theme] = array_merge($cache[$theme], variable_get('theme_settings', array()));
+    $cache[$theme]->setData(NestedArray::mergeDeep($cache[$theme]->get(), config('system.theme.global')->get()));
 
     if ($theme) {
-      // Get the saved theme-specific settings from the database.
-      $cache[$theme] = array_merge($cache[$theme], variable_get('theme_' . $theme . '_settings', array()));
+      // Get the saved theme-specific settings from the configuration system.
+      $cache[$theme]->setData(NestedArray::mergeDeep($cache[$theme]->get(), config($theme . '.settings')->get()));
 
       // If the theme does not support a particular feature, override the global
       // setting and set the value to NULL.
       if (!empty($theme_object->info['features'])) {
-        foreach ($features as $feature) {
+        foreach ($default_config['features'] as $feature => $enabled) {
           if (!in_array($feature, $theme_object->info['features'])) {
-            $cache[$theme]['toggle_' . $feature] = NULL;
+            $cache[$theme]->set('features.' . $feature, NULL);
           }
         }
       }
 
       // Generate the path to the logo image.
-      if ($cache[$theme]['toggle_logo']) {
-        if ($cache[$theme]['default_logo']) {
-          $cache[$theme]['logo'] = file_create_url(dirname($theme_object->filename) . '/logo.png');
+      if ($cache[$theme]->get('features.logo')) {
+        $logo_path = $cache[$theme]->get('logo.path');
+        if ($cache[$theme]->get('logo.use_default')) {
+          $cache[$theme]->set('logo.url', file_create_url(dirname($theme_object->filename) . '/logo.png'));
         }
-        elseif ($cache[$theme]['logo_path']) {
-          $cache[$theme]['logo'] = file_create_url($cache[$theme]['logo_path']);
+        elseif ($logo_path) {
+          $cache[$theme]->set('logo.url', file_create_url($logo_path));
         }
       }
 
       // Generate the path to the favicon.
-      if ($cache[$theme]['toggle_favicon']) {
-        if ($cache[$theme]['default_favicon']) {
+      if ($cache[$theme]->get('features.favicon')) {
+        $favicon_path = $cache[$theme]->get('favicon.path');
+        if ($cache[$theme]->get('favicon.use_default')) {
           if (file_exists($favicon = dirname($theme_object->filename) . '/favicon.ico')) {
-            $cache[$theme]['favicon'] = file_create_url($favicon);
+            $cache[$theme]->set('favicon.url', file_create_url($favicon));
           }
           else {
-            $cache[$theme]['favicon'] = file_create_url('core/misc/favicon.ico');
+            $cache[$theme]->set('favicon.url', file_create_url('core/misc/favicon.ico'));
           }
         }
-        elseif ($cache[$theme]['favicon_path']) {
-          $cache[$theme]['favicon'] = file_create_url($cache[$theme]['favicon_path']);
+        elseif ($favicon_path) {
+          $cache[$theme]->set('favicon.url', file_create_url($favicon_path));
         }
         else {
-          $cache[$theme]['toggle_favicon'] = FALSE;
+          $cache[$theme]->set('features.favicon', FALSE);
         }
       }
     }
   }
 
-  return isset($cache[$theme][$setting_name]) ? $cache[$theme][$setting_name] : NULL;
+  return $cache[$theme]->get($setting_name);
+}
+
+/**
+ * Converts format of old theme-configuration to the format of yml-configuration.
+ *
+ * @param $old_config
+ *   The configuration loaded from old theme configuration
+ * @return
+ *   Configuration array compatible to yml-configuration
+ *
+ * @todo Make this function obsolete
+ */
+function theme_convert_variables_to_config($old_config) {
+  $new_config = array();
+
+  foreach ($old_config as $key => $value) {
+    if ($key == 'logo') {
+      $new_config['logo']['url'] = $value;
+    }
+    else if ($key == 'default_logo') {
+      $new_config['logo']['use_default'] = $value;
+    }
+    else if ($key == 'logo_path') {
+      $new_config['logo']['path'] = $value;
+    }
+    else if ($key == 'favicon') {
+      $new_config['favicon']['url'] = $value;
+    }
+    else if ($key == 'default_favicon') {
+      $new_config['favicon']['use_default'] = $value;
+    }
+    else if ($key == 'favicon_path') {
+      $new_config['favicon']['path'] = $value;
+    }
+    else if ($key == 'favicon_mimetype') {
+      $new_config['favicon']['mimetype'] = $value;
+    }
+    else if (substr($key, 0, 7) == 'toggle_') {
+      $new_config['features'][substr($key, 7)] = $value;
+    }
+    else if (!in_array($key, array('theme', 'logo_upload'))) {
+      $new_config[$key] = $value;
+    }
+  }
+
+  return $new_config;
 }
 
 /**
@@ -1435,7 +1493,7 @@ function theme_enable($theme_list) {
  */
 function theme_disable($theme_list) {
   // Don't disable the default theme.
-  if ($pos = array_search(variable_get('theme_default', 'stark'), $theme_list) !== FALSE) {
+  if ($pos = array_search(config('system.theme')->get('default'), $theme_list) !== FALSE) {
     unset($theme_list[$pos]);
     if (empty($theme_list)) {
       return;
@@ -2445,9 +2503,9 @@ function template_preprocess_html(&$variables) {
   $variables['html_attributes']['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
 
   // Add favicon.
-  if (theme_get_setting('toggle_favicon')) {
-    $favicon = theme_get_setting('favicon');
-    $type = theme_get_setting('favicon_mimetype');
+  if (theme_get_setting('features.favicon')) {
+    $favicon = theme_get_setting('favicon.url');
+    $type = theme_get_setting('favicon.mimetype');
     drupal_add_html_head_link(array('rel' => 'shortcut icon', 'href' => drupal_strip_dangerous_protocols($favicon), 'type' => $type));
   }
 
@@ -2553,12 +2611,12 @@ function template_preprocess_page(&$variables) {
   $variables['feed_icons']        = drupal_get_feeds();
   $variables['language']          = $language_interface;
   $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
-  $variables['logo']              = theme_get_setting('logo');
-  $variables['main_menu']         = theme_get_setting('toggle_main_menu') ? menu_main_menu() : array();
-  $variables['secondary_menu']    = theme_get_setting('toggle_secondary_menu') ? menu_secondary_menu() : array();
+  $variables['logo']              = theme_get_setting('logo.url');
+  $variables['main_menu']         = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
+  $variables['secondary_menu']    = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
   $variables['action_links']      = menu_local_actions();
-  $variables['site_name']         = (theme_get_setting('toggle_name') ? check_plain($site_config->get('name')) : '');
-  $variables['site_slogan']       = (theme_get_setting('toggle_slogan') ? filter_xss_admin($site_config->get('slogan')) : '');
+  $variables['site_name']         = (theme_get_setting('features.name') ? check_plain($site_config->get('name')) : '');
+  $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_config->get('slogan')) : '');
   $variables['tabs']              = menu_local_tabs();
 
   if ($node = menu_get_object()) {
@@ -2714,9 +2772,9 @@ function template_preprocess_maintenance_page(&$variables) {
   $regions = $theme_data[$theme]->info['regions'];
 
   // Add favicon
-  if (theme_get_setting('toggle_favicon')) {
-    $favicon = theme_get_setting('favicon');
-    $type = theme_get_setting('favicon_mimetype');
+  if (theme_get_setting('features.favicon')) {
+    $favicon = theme_get_setting('favicon.url');
+    $type = theme_get_setting('favicon.mimetype');
     drupal_add_html_head_link(array('rel' => 'shortcut icon', 'href' => drupal_strip_dangerous_protocols($favicon), 'type' => $type));
   }
 
@@ -2763,12 +2821,12 @@ function template_preprocess_maintenance_page(&$variables) {
   $variables['help']              = '';
   $variables['language']          = $language_interface;
   $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
-  $variables['logo']              = theme_get_setting('logo');
+  $variables['logo']              = theme_get_setting('logo.url');
   $variables['messages']          = $variables['show_messages'] ? theme('status_messages') : '';
   $variables['main_menu']         = array();
   $variables['secondary_menu']    = array();
-  $variables['site_name']         = (theme_get_setting('toggle_name') ? check_plain($site_name) : '');
-  $variables['site_slogan']       = (theme_get_setting('toggle_slogan') ? filter_xss_admin($site_slogan) : '');
+  $variables['site_name']         = (theme_get_setting('features.name') ? check_plain($site_name) : '');
+  $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_slogan) : '');
   $variables['tabs']              = '';
   $variables['title']             = drupal_get_title();
 
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index 52b6c40..cbb0c42 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -50,7 +50,11 @@ function _drupal_maintenance_theme() {
     //   Stark otherwise. Since there is no low-level access to configuration
     //   currently, we only consult settings.php and fall back to Bartik
     //   otherwise, as it looks generic enough and way more user-friendly.
-    $custom_theme = variable_get('maintenance_theme', variable_get('theme_default', 'bartik'));
+    $config = config('system.theme');
+    $custom_theme = $config->get('maintenance');
+    if (empty($custom_theme)) {
+      $custom_theme = $config->get('default');
+    }
   }
 
   // Ensure that system.module is loaded.
diff --git a/core/modules/block/block.admin.inc b/core/modules/block/block.admin.inc
index aa018da..d5a8013 100644
--- a/core/modules/block/block.admin.inc
+++ b/core/modules/block/block.admin.inc
@@ -307,8 +307,9 @@ function block_admin_configure($form, &$form_state, $module, $delta) {
     '#tree' => TRUE,
   );
 
-  $theme_default = variable_get('theme_default', 'stark');
-  $admin_theme = variable_get('admin_theme');
+  $config = config('system.theme');
+  $theme_default = $config->get('default');
+  $admin_theme = $config->get('admin');
   foreach (list_themes() as $key => $theme) {
     // Only display enabled themes
     if ($theme->status) {
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index db80556..15cd3fa 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -63,7 +63,7 @@ function block_help($path, $arg) {
       return '<p>' . t('Use this page to create a new custom block.') . '</p>';
   }
   if ($arg[0] == 'admin' && $arg[1] == 'structure' && $arg['2'] == 'block' && (empty($arg[3]) || $arg[3] == 'list')) {
-    $demo_theme = !empty($arg[4]) ? $arg[4] : variable_get('theme_default', 'stark');
+    $demo_theme = !empty($arg[4]) ? $arg[4] : config('system.theme')->get('default');
     $themes = list_themes();
     $output = '<p>' . t('This page provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions. Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. Remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page. Click the <em>configure</em> link next to each block to configure its specific title and visibility settings.') . '</p>';
     $output .= '<p>' . l(t('Demonstrate block regions (@theme)', array('@theme' => $themes[$demo_theme]->info['name'])), 'admin/structure/block/demo/' . $demo_theme) . '</p>';
@@ -103,7 +103,7 @@ function block_permission() {
  * Implements hook_menu().
  */
 function block_menu() {
-  $default_theme = variable_get('theme_default', 'stark');
+  $default_theme = config('system.theme')->get('default');
   $items['admin/structure/block'] = array(
     'title' => 'Blocks',
     'description' => 'Configure what block content appears in your site\'s sidebars and other regions.',
@@ -306,7 +306,7 @@ function block_page_build(&$page) {
       $page['page_top']['backlink'] = array(
         '#type' => 'link',
         '#title' => t('Exit block region demonstration'),
-        '#href' => 'admin/structure/block' . (variable_get('theme_default', 'stark') == $theme ? '' : '/list/' . $theme),
+        '#href' => 'admin/structure/block' . (config('system.theme')->get('default') == $theme ? '' : '/list/' . $theme),
         // Add the "overlay-restore" class to indicate this link should restore
         // the context in which the region demonstration page was opened.
         '#options' => array('attributes' => array('class' => array('block-demo-backlink', 'overlay-restore'))),
@@ -674,7 +674,7 @@ function block_theme_initialize($theme) {
   // Initialize theme's blocks if none already registered.
   $has_blocks = (bool) db_query_range('SELECT 1 FROM {block} WHERE theme = :theme', 0, 1, array(':theme' => $theme))->fetchField();
   if (!$has_blocks) {
-    $default_theme = variable_get('theme_default', 'stark');
+    $default_theme = config('system.theme')->get('default');
     // Apply only to new theme's visible regions.
     $regions = system_region_list($theme, REGIONS_VISIBLE);
     $result = db_query("SELECT * FROM {block} WHERE theme = :theme", array(':theme' => $default_theme), array('fetch' => PDO::FETCH_ASSOC));
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockHiddenRegionTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockHiddenRegionTest.php
index 0c3186c..d0bf309 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockHiddenRegionTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockHiddenRegionTest.php
@@ -29,7 +29,7 @@ class BlockHiddenRegionTest extends WebTestBase {
       ->key(array(
         'module' => 'search',
         'delta' => 'form',
-        'theme' => variable_get('theme_default', 'stark'),
+        'theme' => config('system.theme')->get('default'),
       ))
       ->fields(array(
         'status' => 1,
@@ -56,7 +56,7 @@ class BlockHiddenRegionTest extends WebTestBase {
     // Enable "block_test_theme" and set it as the default theme.
     $theme = 'block_test_theme';
     theme_enable(array($theme));
-    variable_set('theme_default', $theme);
+    config('system.theme')->set('default', $theme)->save();
     menu_router_rebuild();
 
     // Ensure that "block_test_theme" is set as the default theme.
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockInvalidRegionTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockInvalidRegionTest.php
index 8882b64..cf9fcee 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockInvalidRegionTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockInvalidRegionTest.php
@@ -32,12 +32,13 @@ class BlockInvalidRegionTest extends WebTestBase {
    * Tests that blocks assigned to invalid regions work correctly.
    */
   function testBlockInInvalidRegion() {
+    $config = config('system.theme');
     // Enable a test block in the default theme and place it in an invalid region.
     db_merge('block')
       ->key(array(
         'module' => 'block_test',
         'delta' => 'test_html_id',
-        'theme' => variable_get('theme_default', 'stark'),
+        'theme' => $config->get('default'),
       ))
       ->fields(array(
         'status' => 1,
@@ -61,7 +62,7 @@ class BlockInvalidRegionTest extends WebTestBase {
       ->key(array(
         'module' => 'block_test',
         'delta' => 'test_html_id',
-        'theme' => variable_get('theme_default', 'stark'),
+        'theme' => $config->get('default'),
       ))
       ->fields(array(
         'region' => 'invalid_region',
diff --git a/core/modules/block/lib/Drupal/block/Tests/NewDefaultThemeBlocksTest.php b/core/modules/block/lib/Drupal/block/Tests/NewDefaultThemeBlocksTest.php
index b17e601..a9f5eba 100644
--- a/core/modules/block/lib/Drupal/block/Tests/NewDefaultThemeBlocksTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/NewDefaultThemeBlocksTest.php
@@ -35,8 +35,9 @@ class NewDefaultThemeBlocksTest extends WebTestBase {
 
     // Ensure no other theme's blocks are in the block table yet.
     $themes = array();
-    $themes['default'] = variable_get('theme_default', 'stark');
-    if ($admin_theme = variable_get('admin_theme')) {
+    $config = config('system.theme');
+    $themes['default'] = $config->get('default');
+    if ($admin_theme = $config->get('admin')) {
       $themes['admin'] = $admin_theme;
     }
     $count = db_query_range('SELECT 1 FROM {block} WHERE theme NOT IN (:themes)', 0, 1, array(':themes' => $themes))->fetchField();
@@ -55,7 +56,7 @@ class NewDefaultThemeBlocksTest extends WebTestBase {
     // the default theme had.
     $new_theme = 'bartik';
     theme_enable(array($new_theme));
-    variable_set('theme_default', $new_theme);
+    config('system.theme')->set('default', $new_theme)->save();
     $result = db_query('SELECT * FROM {block} WHERE theme = :theme', array(':theme' => $new_theme));
     foreach ($result as $block) {
       unset($block->theme, $block->bid);
diff --git a/core/modules/color/lib/Drupal/color/Tests/ColorTest.php b/core/modules/color/lib/Drupal/color/Tests/ColorTest.php
index 3bc95d3..5ba4a1e 100644
--- a/core/modules/color/lib/Drupal/color/Tests/ColorTest.php
+++ b/core/modules/color/lib/Drupal/color/Tests/ColorTest.php
@@ -68,7 +68,7 @@ class ColorTest extends WebTestBase {
    * Tests the Color module functionality using the given theme.
    */
   function _testColor($theme, $test_values) {
-    variable_set('theme_default', $theme);
+    config('system.theme')->set('default', $theme)->save();
     $settings_path = 'admin/appearance/settings/' . $theme;
 
     $this->drupalLogin($this->big_user);
@@ -114,7 +114,7 @@ class ColorTest extends WebTestBase {
    * Tests whether the provided color is valid.
    */
   function testValidColor() {
-    variable_set('theme_default', 'bartik');
+    config('system.theme')->set('default', 'bartik')->save();
     $settings_path = 'admin/appearance/settings/bartik';
 
     $this->drupalLogin($this->big_user);
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index dfa156d..ee7d0f2 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -2130,7 +2130,7 @@ function template_preprocess_comment(&$variables) {
   $variables['changed'] = format_date($comment->changed);
 
   $variables['new'] = !empty($comment->new) ? t('new') : '';
-  $variables['user_picture'] = theme_get_setting('toggle_comment_user_picture') ? theme('user_picture', array('account' => $comment)) : '';
+  $variables['user_picture'] = theme_get_setting('features.comment_user_picture') ? theme('user_picture', array('account' => $comment)) : '';
   $variables['signature'] = $comment->signature;
 
   $uri = entity_uri('comment', $comment);
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentInterfaceTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentInterfaceTest.php
index b7f42ae..91fdf2c 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentInterfaceTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentInterfaceTest.php
@@ -430,7 +430,7 @@ class CommentInterfaceTest extends CommentTestBase {
   function testCommentLinks() {
     // Bartik theme alters comment links, so use a different theme.
     theme_enable(array('stark'));
-    variable_set('theme_default', 'stark');
+    config('system.theme')->set('default', 'stark')->save();
 
     // Remove additional user permissions from $this->web_user added by setUp(),
     // since this test is limited to anonymous and authenticated roles only.
diff --git a/core/modules/node/lib/Drupal/node/Tests/NodeBlockFunctionalTest.php b/core/modules/node/lib/Drupal/node/Tests/NodeBlockFunctionalTest.php
index 6ff9b72..a32fe7c 100644
--- a/core/modules/node/lib/Drupal/node/Tests/NodeBlockFunctionalTest.php
+++ b/core/modules/node/lib/Drupal/node/Tests/NodeBlockFunctionalTest.php
@@ -115,13 +115,14 @@ class NodeBlockFunctionalTest extends NodeTestBase {
     $this->assertText($node4->label(), t('Node found in block.'));
 
     // Create the custom block.
+    $theme_config = config('system.theme');
     $custom_block = array();
     $custom_block['info'] = $this->randomName();
     $custom_block['title'] = $this->randomName();
     $custom_block['types[article]'] = TRUE;
     $custom_block['body[value]'] = $this->randomName(32);
-    $custom_block['regions[' . variable_get('theme_default', 'stark') . ']'] = 'content';
-    if ($admin_theme = variable_get('admin_theme')) {
+    $custom_block['regions[' . $theme_config->get('default') . ']'] = 'content';
+    if ($admin_theme = $theme_config->get('admin')) {
       $custom_block['regions[' . $admin_theme . ']'] = 'content';
     }
     $this->drupalPost('admin/structure/block/add', $custom_block, t('Save block'));
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 3d83cd4..3731a23 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -1421,7 +1421,7 @@ function template_preprocess_node(&$variables) {
   if (variable_get('node_submitted_' . $node->type, TRUE)) {
     $variables['display_submitted'] = TRUE;
     $variables['submitted'] = t('Submitted by !username on !datetime', array('!username' => $variables['name'], '!datetime' => $variables['date']));
-    $variables['user_picture'] = theme_get_setting('toggle_node_user_picture') ? theme('user_picture', array('account' => $node)) : '';
+    $variables['user_picture'] = theme_get_setting('features.node_user_picture') ? theme('user_picture', array('account' => $node)) : '';
   }
   else {
     $variables['display_submitted'] = FALSE;
diff --git a/core/modules/openid/lib/Drupal/openid/Tests/OpenIDTestBase.php b/core/modules/openid/lib/Drupal/openid/Tests/OpenIDTestBase.php
index 302c159..8d7140d 100644
--- a/core/modules/openid/lib/Drupal/openid/Tests/OpenIDTestBase.php
+++ b/core/modules/openid/lib/Drupal/openid/Tests/OpenIDTestBase.php
@@ -27,7 +27,7 @@ abstract class OpenIDTestBase extends WebTestBase {
       ->key(array(
         'module' => 'user',
         'delta' => 'login',
-        'theme' => variable_get('theme_default', 'stark'),
+        'theme' => config('system.theme')->get('default'),
       ))
       ->fields(array(
         'status' => 1,
diff --git a/core/modules/shortcut/lib/Drupal/shortcut/Tests/ShortcutLinksTest.php b/core/modules/shortcut/lib/Drupal/shortcut/Tests/ShortcutLinksTest.php
index 278b1e0..20f649d 100644
--- a/core/modules/shortcut/lib/Drupal/shortcut/Tests/ShortcutLinksTest.php
+++ b/core/modules/shortcut/lib/Drupal/shortcut/Tests/ShortcutLinksTest.php
@@ -62,7 +62,7 @@ class ShortcutLinksTest extends ShortcutTestBase {
    */
   function testShortcutQuickLink() {
     theme_enable(array('seven'));
-    variable_set('admin_theme', 'seven');
+    config('system.theme')->set('admin', 'seven')->save();
     variable_set('node_admin_theme', TRUE);
     $this->drupalGet($this->set->links[0]['link_path']);
     $this->assertRaw(t('Remove from %title shortcuts', array('%title' => $this->set->title)), '"Add to shortcuts" link properly switched to "Remove from shortcuts".');
@@ -120,7 +120,7 @@ class ShortcutLinksTest extends ShortcutTestBase {
    */
   function testNoShortcutLink() {
     // Change to a theme that displays shortcuts.
-    variable_set('theme_default', 'seven');
+    config('system.theme')->set('default', 'seven')->save();
 
     $this->drupalGet('page-that-does-not-exist');
     $this->assertNoRaw('add-shortcut', t('Add to shortcuts link was not shown on a page not found.'));
diff --git a/core/modules/shortcut/shortcut.module b/core/modules/shortcut/shortcut.module
index 27eb8c2..7ebc28c 100644
--- a/core/modules/shortcut/shortcut.module
+++ b/core/modules/shortcut/shortcut.module
@@ -690,7 +690,7 @@ function shortcut_preprocess_page(&$variables) {
       $link_path = 'admin/config/user-interface/shortcut/link/' . $mlid . '/delete';
     }
 
-    if (theme_get_setting('shortcut_module_link')) {
+    if (theme_get_setting('features.shortcut_module_link')) {
       $variables['title_suffix']['add_or_remove_shortcut'] = array(
         '#attached' => array(
           'css' => array(
diff --git a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
index 3df7347..b7111f7 100644
--- a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
+++ b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
@@ -83,7 +83,7 @@ class StatisticsReportsTest extends StatisticsTestBase {
 
     // Configure and save the block.
     $block = block_load('statistics', 'popular');
-    $block->theme = variable_get('theme_default', 'stark');
+    $block->theme = config('system.theme')->get('default');
     $block->status = 1;
     $block->pages = '';
     $block->region = 'sidebar_first';
diff --git a/core/modules/system/config/system.theme.global.yml b/core/modules/system/config/system.theme.global.yml
new file mode 100644
index 0000000..fca8fd2
--- /dev/null
+++ b/core/modules/system/config/system.theme.global.yml
@@ -0,0 +1,19 @@
+favicon:
+    mimetype: image/vnd.microsoft.icon
+    path: ''
+    url: ''
+    use_default: '1'
+features:
+    comment_user_picture: '1'
+    comment_user_verification: '1'
+    favicon: '1'
+    logo: '1'
+    name: '1'
+    node_user_picture: '1'
+    main_menu: '1'
+    secondary_menu: '1'
+    slogan: '1'
+logo:
+    path: ''
+    url: ''
+    use_default: '1'
diff --git a/core/modules/system/config/system.theme.yml b/core/modules/system/config/system.theme.yml
new file mode 100644
index 0000000..5ec84d7
--- /dev/null
+++ b/core/modules/system/config/system.theme.yml
@@ -0,0 +1,3 @@
+admin: '0'
+default: stark
+maintenance: ''
diff --git a/core/modules/system/lib/Drupal/system/Tests/Ajax/FrameworkTest.php b/core/modules/system/lib/Drupal/system/Tests/Ajax/FrameworkTest.php
index d8748bc..6207df5 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Ajax/FrameworkTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Ajax/FrameworkTest.php
@@ -154,7 +154,7 @@ class FrameworkTest extends AjaxTestBase {
     // The test theme overrides system.base.css without an implementation,
     // thereby removing it.
     theme_enable(array('test_theme'));
-    variable_set('theme_default', 'test_theme');
+    config('system.theme')->set('default', 'test_theme')->save();
 
     // This gets the form, and emulates an Ajax submission on it, including
     // adding markup to the HEAD and BODY for any lazy loaded JS/CSS files.
diff --git a/core/modules/system/lib/Drupal/system/Tests/Batch/PageTest.php b/core/modules/system/lib/Drupal/system/Tests/Batch/PageTest.php
index bef4812..2db6093 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Batch/PageTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Batch/PageTest.php
@@ -31,8 +31,10 @@ class PageTest extends WebTestBase {
   function testBatchProgressPageTheme() {
     // Make sure that the page which starts the batch (an administrative page)
     // is using a different theme than would normally be used by the batch API.
-    variable_set('theme_default', 'bartik');
-    variable_set('admin_theme', 'seven');
+    config('system.theme')
+      ->set('default', 'bartik')
+      ->set('admin', 'seven')
+      ->save();
     // Log in as an administrator who can see the administrative theme.
     $admin_user = $this->drupalCreateUser(array('view the administration theme'));
     $this->drupalLogin($admin_user);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/RouterTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/RouterTest.php
index 11db04e..f297af8 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/RouterTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/RouterTest.php
@@ -29,8 +29,10 @@ class RouterTest extends WebTestBase {
     // Make the tests below more robust by explicitly setting the default theme
     // and administrative theme that they expect.
     theme_enable(array('bartik'));
-    variable_set('theme_default', 'bartik');
-    variable_set('admin_theme', 'seven');
+    config('system.theme')
+      ->set('default', 'bartik')
+      ->set('admin', 'seven')
+      ->save();
     theme_disable(array('stark'));
 
     // Enable navigation menu block.
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php b/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
index 30d8422..e3d8257 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/ThemeTest.php
@@ -165,7 +165,8 @@ class ThemeTest extends WebTestBase {
    */
   function testAdministrationTheme() {
     theme_enable(array('stark'));
-    variable_set('theme_default', 'stark');
+    $config = config('system.theme');
+    $config->set('default', 'stark')->save();
     // Enable an administration theme and show it on the node admin pages.
     $edit = array(
       'admin_theme' => 'seven',
@@ -198,7 +199,7 @@ class ThemeTest extends WebTestBase {
     $this->assertRaw('core/themes/stark', t('Site default theme used on the add content page.'));
 
     // Reset to the default theme settings.
-    variable_set('theme_default', 'bartik');
+    $config->set('default', 'bartik')->save();
     $edit = array(
       'admin_theme' => '0',
       'node_admin_theme' => FALSE,
@@ -220,7 +221,7 @@ class ThemeTest extends WebTestBase {
     theme_enable(array('bartik'));
     $this->drupalGet('admin/appearance');
     $this->clickLink(t('Set default'));
-    $this->assertEqual(variable_get('theme_default', ''), 'bartik');
+    $this->assertEqual(config('system.theme')->get('default'), 'bartik');
 
     // Test the default theme on the secondary links (blocks admin page).
     $this->drupalGet('admin/structure/block');
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
index 4be9dd5..475255b 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
@@ -124,7 +124,7 @@ class ThemeTest extends WebTestBase {
    * Ensures a themes template is overrideable based on the 'template' filename.
    */
   function testTemplateOverride() {
-    variable_set('theme_default', 'test_theme');
+    config('system.theme')->set('default', 'test_theme')->save();
     $this->drupalGet('theme-test/template-test');
     $this->assertText('Success: Template overridden.', t('Template overridden by defined \'template\' filename.'));
   }
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 2947245..774e6af 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -8,6 +8,7 @@
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Drupal\Component\Utility\NestedArray;
 
 /**
  * Menu callback; Provide the administration overview page.
@@ -117,7 +118,7 @@ function system_themes_page() {
   $themes = system_rebuild_theme_data();
   uasort($themes, 'system_sort_modules_by_info_name');
 
-  $theme_default = variable_get('theme_default', 'stark');
+  $theme_default = config('system.theme')->get('default');
   $theme_groups  = array();
 
   foreach ($themes as &$theme) {
@@ -240,12 +241,13 @@ function system_themes_admin_form($form, &$form_state, $theme_options) {
     '#type' => 'fieldset',
     '#title' => t('Administration theme'),
   );
+  $admin_theme = config('system.theme')->get('admin');
   $form['admin_theme']['admin_theme'] = array(
     '#type' => 'select',
     '#options' => array(0 => t('Default theme')) + $theme_options,
     '#title' => t('Administration theme'),
     '#description' => t('Choose "Default theme" to always use the same theme as the rest of the site.'),
-    '#default_value' => variable_get('admin_theme', 0),
+    '#default_value' => empty($admin_theme) ? 0 : $admin_theme,
   );
   $form['admin_theme']['actions'] = array('#type' => 'actions');
   $form['admin_theme']['actions']['submit'] = array(
@@ -260,7 +262,7 @@ function system_themes_admin_form($form, &$form_state, $theme_options) {
  */
 function system_themes_admin_form_submit($form, &$form_state) {
   drupal_set_message(t('The configuration options have been saved.'));
-  variable_set('admin_theme', $form_state['values']['admin_theme']);
+  config('system.theme')->set('admin', $form_state['values']['admin_theme'])->save();
 }
 
 /**
@@ -296,7 +298,7 @@ function system_theme_disable() {
 
     // Check if the specified theme is one recognized by the system.
     if (!empty($themes[$theme])) {
-      if ($theme == variable_get('theme_default', 'stark')) {
+      if ($theme == config('system.theme')->get('default')) {
         // Don't disable the default theme.
         drupal_set_message(t('%theme is the default theme and cannot be disabled.', array('%theme' => $themes[$theme]->info['name'])), 'error');
       }
@@ -329,7 +331,8 @@ function system_theme_default() {
        theme_enable(array($theme));
       }
       // Set the default theme.
-      variable_set('theme_default', $theme);
+      $config = config('system.theme');
+      $config->set('default', $theme)->save();
 
       // Rebuild the menu. This duplicates the menu_router_rebuild() in
       // theme_enable(). However, modules must know the current default theme in
@@ -341,7 +344,7 @@ function system_theme_default() {
 
       // The status message depends on whether an admin theme is currently in use:
       // a value of 0 means the admin theme is set to be the default theme.
-      $admin_theme = variable_get('admin_theme', 0);
+      $admin_theme = $config->get('admin');
       if ($admin_theme != 0 && $admin_theme != $theme) {
         drupal_set_message(t('Please note that the administration theme is still set to the %admin_theme theme; consequently, the theme on this page remains unchanged. All non-administrative sections of the site, however, will show the selected %selected_theme theme by default.', array(
           '%admin_theme' => $themes[$admin_theme]->info['name'],
@@ -368,20 +371,24 @@ function system_theme_default() {
  * @return
  *   The form structure.
  * @ingroup forms
+ * @see system_theme_settings_validate()
  * @see system_theme_settings_submit()
  */
 function system_theme_settings($form, &$form_state, $key = '') {
   // Default settings are defined in theme_get_setting() in includes/theme.inc
   if ($key) {
     $var = 'theme_' . $key . '_settings';
+    $config_key = $key . '.settings';
     $themes = list_themes();
     $features = $themes[$key]->info['features'];
   }
   else {
     $var = 'theme_settings';
+    $config_key = 'system.theme.global';
   }
 
   $form['var'] = array('#type' => 'hidden', '#value' => $var);
+  $form['config_key'] = array('#type' => 'hidden', '#value' => $config_key);
 
   // Toggle settings
   $toggles = array(
@@ -414,7 +421,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
   );
   foreach ($toggles as $name => $title) {
     if ((!$key) || in_array($name, $features)) {
-      $form['theme_settings']['toggle_' . $name] = array('#type' => 'checkbox', '#title' => $title, '#default_value' => theme_get_setting('toggle_' . $name, $key));
+      $form['theme_settings']['toggle_' . $name] = array('#type' => 'checkbox', '#title' => $title, '#default_value' => theme_get_setting('features.' . $name, $key));
       // Disable checkboxes for features not supported in the current configuration.
       if (isset($disabled['toggle_' . $name])) {
         $form['theme_settings']['toggle_' . $name]['#disabled'] = TRUE;
@@ -438,7 +445,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $form['logo']['default_logo'] = array(
       '#type' => 'checkbox',
       '#title' => t('Use the default logo supplied by the theme'),
-      '#default_value' => theme_get_setting('default_logo', $key),
+      '#default_value' => theme_get_setting('logo.use_default', $key),
       '#tree' => FALSE,
     );
     $form['logo']['settings'] = array(
@@ -453,7 +460,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $form['logo']['settings']['logo_path'] = array(
       '#type' => 'textfield',
       '#title' => t('Path to custom logo'),
-      '#default_value' => theme_get_setting('logo_path', $key),
+      '#default_value' => theme_get_setting('logo.path', $key),
     );
     $form['logo']['settings']['logo_upload'] = array(
       '#type' => 'file',
@@ -472,7 +479,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $form['favicon']['default_favicon'] = array(
       '#type' => 'checkbox',
       '#title' => t('Use the default shortcut icon supplied by the theme'),
-      '#default_value' => theme_get_setting('default_favicon', $key),
+      '#default_value' => theme_get_setting('favicon.use_default', $key),
     );
     $form['favicon']['settings'] = array(
       '#type' => 'container',
@@ -486,7 +493,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $form['favicon']['settings']['favicon_path'] = array(
       '#type' => 'textfield',
       '#title' => t('Path to custom icon'),
-      '#default_value' => theme_get_setting('favicon_path', $key),
+      '#default_value' => theme_get_setting('favicon.path', $key),
     );
     $form['favicon']['settings']['favicon_upload'] = array(
       '#type' => 'file',
@@ -580,12 +587,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     }
   }
 
-  $form = system_settings_form($form);
-  // We don't want to call system_settings_form_submit(), so change #submit.
-  array_pop($form['#submit']);
-  $form['#submit'][] = 'system_theme_settings_submit';
-  $form['#validate'][] = 'system_theme_settings_validate';
-  return $form;
+  return system_config_form($form, $form_state);
 }
 
 /**
@@ -678,10 +680,13 @@ function _system_theme_settings_validate_path($path) {
  * Process system_theme_settings form submissions.
  */
 function system_theme_settings_submit($form, &$form_state) {
+  $config = config($form_state['values']['config_key']);
+
   // Exclude unnecessary elements before saving.
   form_state_values_clean($form_state);
   $key = $form_state['values']['var'];
   unset($form_state['values']['var']);
+  unset($form_state['values']['config_key']);
 
   $values = $form_state['values'];
 
@@ -715,9 +720,10 @@ function system_theme_settings_submit($form, &$form_state) {
     $values['favicon_mimetype'] = file_get_mimetype($values['favicon_path']);
   }
 
-  variable_set($key, $values);
-  drupal_set_message(t('The configuration options have been saved.'));
-
+  // Merge form values into theme's configuration data in case there is
+  // configuration not exposed on system_theme_settings().
+  $new_config =  theme_convert_variables_to_config($values);
+  $config->setData(NestedArray::mergeDeep($config->get(), $new_config))->save();
   cache_invalidate(array('content' => TRUE));
 }
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 96c02c3..d03af81 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -507,7 +507,7 @@ function system_requirements($phase) {
  */
 function system_install() {
   // Enable the default theme.
-  variable_set('theme_default', 'stark');
+  config('system.theme')->set('default', 'stark')->save();
   db_update('system')
     ->fields(array('status' => 1))
     ->condition('type', 'theme')
@@ -1998,6 +1998,32 @@ function system_update_8014() {
 }
 
 /**
+ * Moves system theme settings from variables to config.
+ */
+function system_update_8015() {
+  $variables = array('theme_settings' => 'system.theme.global');
+  $themes = list_themes();
+  foreach ($themes as $theme) {
+    $variables['theme_' . $theme->name . '_settings'] = $theme->name . '.settings';
+  }
+
+  foreach ($variables as $old_key => $new_key) {
+    $config = theme_convert_variables_to_config(variable_get($old_key, array()));
+    $new_config = config($new_key);
+    foreach ($config as $key => $value) {
+      $new_config->set($key, $value);
+    }
+    $new_config->save();
+  }
+
+  update_variables_to_config('system.theme', array(
+    'admin_theme' => 'admin',
+    'theme_default' => 'default',
+    'maintenance_theme' => 'maintenance',
+  ));
+}
+
+/**
  * @} End of "defgroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index a530c30..98e86ba 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -237,7 +237,7 @@ function system_permission() {
     ),
     'view the administration theme' => array(
       'title' => t('View the administration theme'),
-      'description' => variable_get('admin_theme') ? '' : t('This is only used when the site is configured to use a separate administration theme on the <a href="@appearance-url">Appearance</a> page.', array('@appearance-url' => url('admin/appearance'))),
+      'description' => config('system.theme')->get('admin') ? '' : t('This is only used when the site is configured to use a separate administration theme on the <a href="@appearance-url">Appearance</a> page.', array('@appearance-url' => url('admin/appearance'))),
     ),
     'access site reports' => array(
       'title' => t('View site reports'),
@@ -2202,7 +2202,7 @@ function system_custom_theme() {
   if ($request = request()) {
     $path = $request->attributes->get('system_path');
     if (user_access('view the administration theme') && path_is_admin($path)) {
-      return variable_get('admin_theme');
+      return config('system.theme')->get('admin');
     }
   }
 }
diff --git a/core/modules/system/tests/modules/menu_test/menu_test.module b/core/modules/system/tests/modules/menu_test/menu_test.module
index 8f24a4f..2440fe6 100644
--- a/core/modules/system/tests/modules/menu_test/menu_test.module
+++ b/core/modules/system/tests/modules/menu_test/menu_test.module
@@ -462,7 +462,7 @@ function menu_test_theme_page_callback($inherited = FALSE) {
 function menu_test_theme_callback($argument) {
   // Test using the variable administrative theme.
   if ($argument == 'use-admin-theme') {
-    return variable_get('admin_theme');
+    return config('system.theme')->get('admin');
   }
   // Test using a theme that exists, but may or may not be enabled.
   elseif ($argument == 'use-stark-theme') {
diff --git a/core/modules/system/theme.api.php b/core/modules/system/theme.api.php
index b98132e..3693b97 100644
--- a/core/modules/system/theme.api.php
+++ b/core/modules/system/theme.api.php
@@ -87,7 +87,7 @@ function hook_form_system_theme_settings_alter(&$form, &$form_state) {
   $form['toggle_breadcrumb'] = array(
     '#type' => 'checkbox',
     '#title' => t('Display the breadcrumb'),
-    '#default_value' => theme_get_setting('toggle_breadcrumb'),
+    '#default_value' => theme_get_setting('features.breadcrumb'),
     '#description'   => t('Show a trail of links from the homepage to the current page.'),
   );
 }
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/ThemeTest.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/ThemeTest.php
index baa5c61..4c763b3 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/ThemeTest.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Tests/ThemeTest.php
@@ -25,8 +25,10 @@ class ThemeTest extends TaxonomyTestBase {
 
     // Make sure we are using distinct default and administrative themes for
     // the duration of these tests.
-    variable_set('theme_default', 'bartik');
-    variable_set('admin_theme', 'seven');
+    config('system.theme')
+      ->set('default', 'bartik')
+      ->set('admin', 'seven')
+      ->save();
 
     // Create and log in as a user who has permission to add and edit taxonomy
     // terms and view the administrative theme.
diff --git a/core/modules/user/lib/Drupal/user/Tests/UserBlocksTests.php b/core/modules/user/lib/Drupal/user/Tests/UserBlocksTests.php
index 8e69750..c1e6553 100644
--- a/core/modules/user/lib/Drupal/user/Tests/UserBlocksTests.php
+++ b/core/modules/user/lib/Drupal/user/Tests/UserBlocksTests.php
@@ -29,7 +29,7 @@ class UserBlocksTests extends WebTestBase {
       ->key(array(
         'module' => 'user',
         'delta' => 'login',
-        'theme' => variable_get('theme_default', 'stark'),
+        'theme' => config('system.theme')->get('default'),
       ))
       ->fields(array(
         'status' => 1,
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index e373062..c3812f97 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -1290,7 +1290,7 @@ function template_preprocess_username(&$variables) {
   $variables['extra'] = '';
   if (empty($account->uid)) {
    $variables['uid'] = 0;
-   if (theme_get_setting('toggle_comment_user_verification')) {
+   if (theme_get_setting('features.comment_user_verification')) {
      $variables['extra'] = ' (' . t('not verified') . ')';
    }
   }
diff --git a/core/themes/bartik/bartik.info b/core/themes/bartik/bartik.info
index c0c206d..e1652c6 100644
--- a/core/themes/bartik/bartik.info
+++ b/core/themes/bartik/bartik.info
@@ -30,4 +30,4 @@ regions[footer_thirdcolumn] = Footer third column
 regions[footer_fourthcolumn] = Footer fourth column
 regions[footer] = Footer
 
-settings[shortcut_module_link] = 0
+settings[features][shortcut_module_link] = 0
diff --git a/core/themes/bartik/color/color.inc b/core/themes/bartik/color/color.inc
index 50ce731..f70450c 100644
--- a/core/themes/bartik/color/color.inc
+++ b/core/themes/bartik/color/color.inc
@@ -6,7 +6,7 @@
  */
 
 // Put the logo path into JavaScript for the live preview.
-drupal_add_js(array('color' => array('logo' => theme_get_setting('logo', 'bartik'))), 'setting');
+drupal_add_js(array('color' => array('logo' => theme_get_setting('logo.url', 'bartik'))), 'setting');
 
 $info = array(
   // Available colors and color labels used in theme.
diff --git a/core/themes/bartik/template.php b/core/themes/bartik/template.php
index 5373c92..b1dbb51 100644
--- a/core/themes/bartik/template.php
+++ b/core/themes/bartik/template.php
@@ -50,8 +50,8 @@ function bartik_process_page(&$variables) {
   }
   // Always print the site name and slogan, but if they are toggled off, we'll
   // just hide them visually.
-  $variables['hide_site_name']   = theme_get_setting('toggle_name') ? FALSE : TRUE;
-  $variables['hide_site_slogan'] = theme_get_setting('toggle_slogan') ? FALSE : TRUE;
+  $variables['hide_site_name']   = theme_get_setting('features.name') ? FALSE : TRUE;
+  $variables['hide_site_slogan'] = theme_get_setting('features.slogan') ? FALSE : TRUE;
   if ($variables['hide_site_name']) {
     // If toggle_name is FALSE, the site_name will be empty, so we rebuild it.
     $variables['site_name'] = check_plain($site_config->get('name'));
@@ -98,8 +98,8 @@ function bartik_process_maintenance_page(&$variables) {
   $site_config = config('system.site');
   // Always print the site name and slogan, but if they are toggled off, we'll
   // just hide them visually.
-  $variables['hide_site_name']   = theme_get_setting('toggle_name') ? FALSE : TRUE;
-  $variables['hide_site_slogan'] = theme_get_setting('toggle_slogan') ? FALSE : TRUE;
+  $variables['hide_site_name']   = theme_get_setting('features.name') ? FALSE : TRUE;
+  $variables['hide_site_slogan'] = theme_get_setting('features.slogan') ? FALSE : TRUE;
   if ($variables['hide_site_name']) {
     // If toggle_name is FALSE, the site_name will be empty, so we rebuild it.
     $variables['site_name'] = check_plain($site_config->get('name'));
diff --git a/core/themes/seven/seven.info b/core/themes/seven/seven.info
index 969f749..69d052d 100644
--- a/core/themes/seven/seven.info
+++ b/core/themes/seven/seven.info
@@ -5,7 +5,7 @@ version = VERSION
 core = 8.x
 stylesheets[screen][] = reset.css
 stylesheets[screen][] = style.css
-settings[shortcut_module_link] = 1
+settings[features][shortcut_module_link] = 1
 regions[content] = Content
 regions[help] = Help
 regions[page_top] = Page top
diff --git a/profiles/minimal/minimal.install b/profiles/minimal/minimal.install
index 2c4cee1..65270ed 100644
--- a/profiles/minimal/minimal.install
+++ b/profiles/minimal/minimal.install
@@ -15,7 +15,7 @@ function minimal_install() {
   // Enable Bartik theme and set it as default theme instead of Stark.
   // @see system_install()
   $default_theme = 'bartik';
-  variable_set('theme_default', $default_theme);
+  config('system.theme')->set('default', $default_theme);
   theme_enable(array($default_theme));
   theme_disable(array('stark'));
 
diff --git a/profiles/standard/standard.install b/profiles/standard/standard.install
index 27faf10..593269d 100644
--- a/profiles/standard/standard.install
+++ b/profiles/standard/standard.install
@@ -71,7 +71,8 @@ function standard_install() {
   // Enable Bartik theme and set it as default theme instead of Stark.
   // @see system_install()
   $default_theme = 'bartik';
-  variable_set('theme_default', $default_theme);
+  $theme_config = config('system.theme');
+  $theme_config->set('default', $default_theme)->save();
   theme_enable(array($default_theme));
   theme_disable(array('stark'));
 
@@ -409,6 +410,6 @@ function standard_install() {
     ->condition('type', 'theme')
     ->condition('name', 'seven')
     ->execute();
-  variable_set('admin_theme', 'seven');
+  $theme_config->set('admin', 'seven')->save();
   variable_set('node_admin_theme', '1');
 }