diff --git a/core/includes/ajax.inc b/core/includes/ajax.inc
index 330d887..026d630 100644
--- a/core/includes/ajax.inc
+++ b/core/includes/ajax.inc
@@ -447,8 +447,7 @@ function ajax_prepare_response($page_callback_result) {
         break;

       case MENU_SITE_OFFLINE:
-        $commands[] = ajax_command_alert(filter_xss_admin(variable_get('maintenance_mode_message',
-          t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => config('system.site')->get('name'))))));
+        $commands[] = ajax_command_alert(filter_xss_admin(t(config('system.maintenance')->get('message'), array('@site' => config('system.site')->get('name')))));
         break;
     }
   }
diff --git a/core/includes/menu.inc b/core/includes/menu.inc
index 5677369..e629f60 100644
--- a/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -3781,7 +3781,7 @@ function _menu_router_save($menu, $masks) {
  */
 function _menu_site_is_offline($check_only = FALSE) {
   // Check if site is in maintenance mode.
-  if (variable_get('maintenance_mode', 0)) {
+  if (config('system.maintenance')->get('mode')) {
     if (user_access('access site in maintenance mode')) {
       // Ensure that the maintenance mode message is displayed only once
       // (allowing for page redirects) and specifically suppress its display on
diff --git a/core/includes/update.inc b/core/includes/update.inc
index acfc0d5..bf0aa54 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -505,9 +505,9 @@ function update_do_one($module, $number, $dependency_map, &$context) {
 function update_batch($start, $redirect = NULL, $url = NULL, $batch = array(), $redirect_callback = 'drupal_goto') {
   // During the update, bring the site offline so that schema changes do not
   // affect visiting users.
-  $_SESSION['maintenance_mode'] = variable_get('maintenance_mode', FALSE);
+  $_SESSION['maintenance_mode'] = config('system.maintenance')->get('mode');
   if ($_SESSION['maintenance_mode'] == FALSE) {
-    variable_set('maintenance_mode', TRUE);
+    config('system.maintenance')->set('mode', TRUE)->save();
   }

   // Resolve any update dependencies to determine the actual updates that will
@@ -578,7 +578,7 @@ function update_finished($success, $results, $operations) {
   // Now that the update is done, we can put the site back online if it was
   // previously in maintenance mode.
   if (isset($_SESSION['maintenance_mode']) && $_SESSION['maintenance_mode'] == FALSE) {
-    variable_set('maintenance_mode', FALSE);
+    config('system.maintenance')->set('mode', FALSE)->save();
     unset($_SESSION['maintenance_mode']);
   }
 }
diff --git a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
index 6485fa1..d4eabfb 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
@@ -39,7 +39,7 @@ class MaintenanceModeSubscriber implements EventSubscriberInterface {
       // Deliver the 503 page.
       drupal_maintenance_theme();
       drupal_set_title(t('Site under maintenance'));
-      $content = theme('maintenance_page', array('content' => filter_xss_admin(variable_get('maintenance_mode_message', t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => config('system.site')->get('name')))))));
+      $content = theme('maintenance_page', array('content' => filter_xss_admin(t(config('system.maintenance')->get('message'), array('@site' => config('system.site')->get('name'))))));
       $response = new Response('Service unavailable', 503);
       $response->setContent($content);
       $event->setResponse($response);
diff --git a/core/modules/openid/lib/Drupal/openid/Tests/OpenIDFunctionalTest.php b/core/modules/openid/lib/Drupal/openid/Tests/OpenIDFunctionalTest.php
index edf7fd8..b84feaf 100644
--- a/core/modules/openid/lib/Drupal/openid/Tests/OpenIDFunctionalTest.php
+++ b/core/modules/openid/lib/Drupal/openid/Tests/OpenIDFunctionalTest.php
@@ -189,7 +189,7 @@ class OpenIDFunctionalTest extends OpenIDTestBase {
     $this->drupalLogout();

     // Enable maintenance mode.
-    variable_set('maintenance_mode', 1);
+    config('system.maintenance')->set('mode', TRUE)->save();

     // Test logging in via the user/login page while the site is offline.
     $edit = array('openid_identifier' => $identity);
diff --git a/core/modules/system/config/system.maintenance.yml b/core/modules/system/config/system.maintenance.yml
new file mode 100644
index 0000000..2b782da
--- /dev/null
+++ b/core/modules/system/config/system.maintenance.yml
@@ -0,0 +1,2 @@
+mode: '0'
+message: @site is currently under maintenance. We should be back shortly. Thank you for your patience.
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index d956f05..b76cb83 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -2222,22 +2222,36 @@ function system_date_time_lookup() {
  * Form builder; Configure the site's maintenance status.
  *
  * @ingroup forms
- * @see system_settings_form()
+ * @see system_site_maintenance_mode_submit()
  */
-function system_site_maintenance_mode() {
+function system_site_maintenance_mode($form, &$form_state) {
+  $config = config('system.maintenance');
   $form['maintenance_mode'] = array(
     '#type' => 'checkbox',
     '#title' => t('Put site into maintenance mode'),
-    '#default_value' => variable_get('maintenance_mode', 0),
+    '#default_value' => $config->get('mode'),
     '#description' => t('Visitors will only see the maintenance mode message. Only users with the "Access site in maintenance mode" <a href="@permissions-url">permission</a> will be able to access the site. Authorized users can log in directly via the <a href="@user-login">user login</a> page.', array('@permissions-url' => url('admin/config/people/permissions'), '@user-login' => url('user'))),
   );
   $form['maintenance_mode_message'] = array(
     '#type' => 'textarea',
     '#title' => t('Message to display when in maintenance mode'),
-    '#default_value' => variable_get('maintenance_mode_message', t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => config('system.site')->get('name')))),
+    '#default_value' => $config->get('message'),
   );

-  return system_settings_form($form);
+  return system_config_form($form, $form_state);
+}
+
+/**
+ * Form builder submit handler. Handle submission for site maintenance settings.
+ *
+ * @ingroup forms
+ * @see system_settings_form()
+ */
+function system_site_maintenance_mode_submit($form, &$form_state) {
+	config('system.maintenance')
+    ->set('mode', $form_state['values']['maintenance_mode'])
+    ->set('message', $form_state['values']['maintenance_mode_message'])
+    ->save();
 }

 /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 14cc390..3356480 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1181,7 +1181,7 @@ function system_cron_access($key) {
     watchdog('cron', 'Cron could not run because an invalid key was used.', array(), WATCHDOG_NOTICE);
     return FALSE;
   }
-  elseif (variable_get('maintenance_mode', 0)) {
+  elseif (config('system.maintenance')->get('mode')) {
     watchdog('cron', 'Cron could not run because the site is in maintenance mode.', array(), WATCHDOG_NOTICE);
     return FALSE;
   }
diff --git a/core/modules/update/update.authorize.inc b/core/modules/update/update.authorize.inc
index 37195e1..2f7bc2b 100644
--- a/core/modules/update/update.authorize.inc
+++ b/core/modules/update/update.authorize.inc
@@ -190,7 +190,7 @@ function update_authorize_update_batch_finished($success, $results) {
       $success = FALSE;
     }
   }
-  $offline = variable_get('maintenance_mode', FALSE);
+  $offline = config('system.maintenance')->get('mode');
   if ($success) {
     // Now that the update completed, we need to clear the cache of available
     // update data and recompute our status, so prevent show bogus results.
@@ -198,7 +198,7 @@ function update_authorize_update_batch_finished($success, $results) {

     // Take the site out of maintenance mode if it was previously that way.
     if ($offline && isset($_SESSION['maintenance_mode']) && $_SESSION['maintenance_mode'] == FALSE) {
-      variable_set('maintenance_mode', FALSE);
+      config('system.maintenance')->set('mode', FALSE)->save();
       $page_message = array(
         'message' => t('Update was completed successfully. Your site has been taken out of maintenance mode.'),
         'type' => 'status',
@@ -257,11 +257,11 @@ function update_authorize_install_batch_finished($success, $results) {
       $success = FALSE;
     }
   }
-  $offline = variable_get('maintenance_mode', FALSE);
+  $offline = config('system.maintenance')->get('mode');
   if ($success) {
     // Take the site out of maintenance mode if it was previously that way.
     if ($offline && isset($_SESSION['maintenance_mode']) && $_SESSION['maintenance_mode'] == FALSE) {
-      variable_set('maintenance_mode', FALSE);
+      config('system.maintenance')->set('mode', FALSE)->save();
       $page_message = array(
         'message' => t('Installation was completed successfully. Your site has been taken out of maintenance mode.'),
         'type' => 'status',
diff --git a/core/modules/update/update.manager.inc b/core/modules/update/update.manager.inc
index 1e4a3d5..5ab1234 100644
--- a/core/modules/update/update.manager.inc
+++ b/core/modules/update/update.manager.inc
@@ -423,9 +423,9 @@ function update_manager_update_ready_form($form, &$form_state) {
  */
 function update_manager_update_ready_form_submit($form, &$form_state) {
   // Store maintenance_mode setting so we can restore it when done.
-  $_SESSION['maintenance_mode'] = variable_get('maintenance_mode', FALSE);
+  $_SESSION['maintenance_mode'] = config('system.maintenance')->get('mode');
   if ($form_state['values']['maintenance_mode'] == TRUE) {
-    variable_set('maintenance_mode', TRUE);
+    config('system.maintenance')->set('mode', TRUE)->save();
   }

   if (!empty($_SESSION['update_manager_update_projects'])) {