diff --git a/core/core.services.yml b/core/core.services.yml
index 36376e2..7700054 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -277,7 +277,7 @@ services:
     arguments: ['%container.modules%', '@cache.bootstrap']
   theme_handler:
     class: Drupal\Core\Extension\ThemeHandler
-    arguments: ['@config.factory', '@module_handler', '@state', '@info_parser', '@logger.channel.default', '@asset.css.collection_optimizer', '@config.installer', '@router.builder']
+    arguments: ['@config.factory', '@module_handler', '@state', '@info_parser', '@logger.channel.default', '@asset.css.collection_optimizer', '@config.installer', '@config.manager', '@router.builder']
   entity.manager:
     class: Drupal\Core\Entity\EntityManager
     arguments: ['@container.namespaces', '@module_handler', '@cache.discovery', '@language_manager', '@string_translation', '@class_resolver', '@typed_data_manager']
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index ba1c257..df83a02 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Config\ConfigInstallerInterface;
+use Drupal\Core\Config\ConfigManagerInterface;
 use Drupal\Core\State\StateInterface;
 use Drupal\Core\Routing\RouteBuilder;
 use Psr\Log\LoggerInterface;
@@ -109,6 +110,13 @@ class ThemeHandler implements ThemeHandlerInterface {
   protected $cssCollectionOptimizer;
 
   /**
+   * The config manager used to uninstall a theme.
+   *
+   * @var \Drupal\Core\Config\ConfigManagerInterface
+   */
+  protected $configManager;
+
+  /**
    * Constructs a new ThemeHandler.
    *
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
@@ -119,20 +127,22 @@ class ThemeHandler implements ThemeHandlerInterface {
    *   The state store.
    * @param \Drupal\Core\Extension\InfoParserInterface $info_parser
    *   The info parser to parse the theme.info.yml files.
-   * @param \Drupal\Core\Asset\AssetCollectionOptimizerInterface $css_collection_optimizer
-   *   The CSS asset collection optimizer service.
    * @param \Psr\Log\LoggerInterface $logger
    *   A logger instance.
+   * @param \Drupal\Core\Asset\AssetCollectionOptimizerInterface $css_collection_optimizer
+   *   The CSS asset collection optimizer service.
    * @param \Drupal\Core\Config\ConfigInstallerInterface $config_installer
    *   (optional) The config installer to install configuration. This optional
    *   to allow the theme handler to work before Drupal is installed and has a
    *   database.
+   * @param \Drupal\Core\Config\ConfigManagerInterface $config_manager
+   *   The config manager used to uninstall a theme.
    * @param \Drupal\Core\Routing\RouteBuilder $route_builder
    *   (optional) The route builder to rebuild the routes if a theme is enabled.
    * @param \Drupal\Core\Extension\ExtensionDiscovery $extension_discovery
    *   (optional) A extension discovery instance (for unit tests).
    */
-  public function __construct(ConfigFactoryInterface $config_factory, ModuleHandlerInterface $module_handler, StateInterface $state, InfoParserInterface $info_parser,LoggerInterface $logger, AssetCollectionOptimizerInterface $css_collection_optimizer = NULL, ConfigInstallerInterface $config_installer = NULL, RouteBuilder $route_builder = NULL, ExtensionDiscovery $extension_discovery = NULL) {
+  public function __construct(ConfigFactoryInterface $config_factory, ModuleHandlerInterface $module_handler, StateInterface $state, InfoParserInterface $info_parser,LoggerInterface $logger, AssetCollectionOptimizerInterface $css_collection_optimizer = NULL, ConfigInstallerInterface $config_installer = NULL, ConfigManagerInterface $config_manager = NULL, RouteBuilder $route_builder = NULL, ExtensionDiscovery $extension_discovery = NULL) {
     $this->configFactory = $config_factory;
     $this->moduleHandler = $module_handler;
     $this->state = $state;
@@ -140,6 +150,7 @@ public function __construct(ConfigFactoryInterface $config_factory, ModuleHandle
     $this->logger = $logger;
     $this->cssCollectionOptimizer = $css_collection_optimizer;
     $this->configInstaller = $config_installer;
+    $this->configManager = $config_manager;
     $this->routeBuilder = $route_builder;
     $this->extensionDiscovery = $extension_discovery;
   }
@@ -368,13 +379,13 @@ public function uninstall(array $theme_list) {
 
     foreach ($theme_list as $key) {
       // Remove all configuration belonging to the theme.
-      \Drupal::service('config.manager')->uninstall('theme', $key);
+      $this->configManager->uninstall('theme', $key);
 
       $extension_config->clear("disabled.theme.$key");
     }
     $extension_config->save();
 
-    $this->moduleHandler->invokeAll('themes_uninstalled', array($theme_list));
+    $this->moduleHandler->invokeAll('themes_uninstalled', [$theme_list]);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
index fc68831..353ab81 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
@@ -44,9 +44,15 @@ public function disable(array $theme_list);
   /**
    * Uninstalls a given list of disabled themes.
    *
+   * Uninstalling a theme removes all related configuration (like blocks) and
+   * invokes the 'themes_uninstalled' hook.
+   *
    * @param array $theme_list
    *   The themes to uninstall.
    *
+   * @throws \InvalidArgumentException
+   *   Thrown when you uninstall an not installed or not disabled theme.
+   *
    * @see hook_themes_uninstalled()
    */
   public function uninstall(array $theme_list);
@@ -150,6 +156,16 @@ public function getName($theme);
   public function getDefault();
 
   /**
+   * Sets a new default theme.
+   *
+   * @param string $theme
+   *   The new default theme.
+   *
+   * @return $this
+   */
+  public function setDefault($theme);
+
+  /**
    * Returns an array of directories for all enabled themes.
    *
    * Useful for tasks such as finding a file that exists in all theme
diff --git a/core/modules/block/src/Tests/BlockTest.php b/core/modules/block/src/Tests/BlockTest.php
index ebd4a7c..abfd375 100644
--- a/core/modules/block/src/Tests/BlockTest.php
+++ b/core/modules/block/src/Tests/BlockTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\block\Tests;
 
+use Drupal\block\Entity\Block;
 use Drupal\Core\Cache\Cache;
 use Drupal\simpletest\WebTestBase;
 use Drupal\Component\Utility\String;
@@ -376,4 +377,25 @@ public function testBlockCacheTags() {
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'MISS');
   }
 
+  /**
+   * Tests that uninstalling a theme removes its block configuration.
+   */
+  public function testUninstallTheme() {
+    /** @var \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler */
+    $theme_handler = \Drupal::service('theme_handler');
+
+    $theme_handler->enable(['seven']);
+    $theme_handler->setDefault('seven');
+    $block = $this->drupalPlaceBlock('system_powered_by_block', ['theme' => 'seven', 'region' => 'help']);
+    $this->drupalGet('<front>');
+    $this->assertText('Powered by Drupal');
+
+    $theme_handler->setDefault('stark');
+    $theme_handler->disable(['seven']);
+    $theme_handler->uninstall(['seven']);
+
+    // Ensure that the block configuration does not exist anymore.
+    $this->assertIdentical(NULL, Block::load($block->id()));
+  }
+
 }
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 59922b7..75987fa 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -1397,6 +1397,42 @@ function hook_module_preuninstall($module) {
 }
 
 /**
+ * Perform necessary actions when themes are enabled.
+ *
+ * @param array $themes
+ *   An array of theme names which are enabled.
+ */
+function hook_themes_enabled(array $themes) {
+  // Add some state entries depending on the theme.
+  foreach ($themes as $theme) {
+    \Drupal::state()->set('example.' . $theme, 'some-value');
+  }
+}
+
+/**
+ * Perform necessary actions when themes are disabled.
+ *
+ * @param array $themes
+ *   An array of theme names which are enabled.
+ */
+function hook_themes_disabled(array $themes) {
+  // Update some state entries depending on the theme.
+  foreach ($themes as $theme) {
+    \Drupal::state()->set('example.' . $theme, 0);
+  }
+}
+
+/**
+ * Perform necessary actions when themes are uninstalled.
+ */
+function hook_themes_uninstalled(array $themes) {
+  // Remove some state entries depending on the theme.
+  foreach ($themes as $theme) {
+    \Drupal::state()->delete('example.' . $theme);
+  }
+}
+
+/**
  * Perform necessary actions after modules are uninstalled.
  *
  * This function differs from hook_uninstall() in that it gives all other