diff --git a/core/core.services.yml b/core/core.services.yml
index afccb31..3ae58c3 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1202,6 +1202,11 @@ services:
     arguments: ['@current_route_match']
     tags:
       - { name: route_processor_outbound, priority: 200 }
+  route_processor_entity_uuid:
+    class: Drupal\Core\RouteProcessor\RouteProcessorEntityUUID
+    arguments: ['@entity.manager']
+    tags:
+      - { name: route_processor_outbound, priority: 100 }
   path_processor_alias:
     class: Drupal\Core\PathProcessor\PathProcessorAlias
     tags:
diff --git a/core/lib/Drupal/Core/Entity/EntityTypeManager.php b/core/lib/Drupal/Core/Entity/EntityTypeManager.php
index 25f9cff..3a24e0e 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeManager.php
@@ -177,20 +177,25 @@ public function getListBuilder($entity_type) {
    * {@inheritdoc}
    */
   public function getFormObject($entity_type, $operation) {
-    if (!$class = $this->getDefinition($entity_type, TRUE)->getFormClass($operation)) {
-      throw new InvalidPluginDefinitionException($entity_type, sprintf('The "%s" entity type did not specify a "%s" form class.', $entity_type, $operation));
-    }
+    if (!isset($this->handlers['form'][$operation][$entity_type])) {
+      if (!$class = $this->getDefinition($entity_type, TRUE)->getFormClass($operation)) {
+        throw new InvalidPluginDefinitionException($entity_type, sprintf('The "%s" entity type did not specify a "%s" form class.', $entity_type, $operation));
+      }
 
-    $form_object = $this->classResolver->getInstanceFromDefinition($class);
+      $form_object = $this->classResolver->getInstanceFromDefinition($class);
+
+      $form_object
+        ->setStringTranslation($this->stringTranslation)
+        ->setModuleHandler($this->moduleHandler)
+        ->setEntityTypeManager($this)
+        ->setOperation($operation)
+        // The entity manager cannot be injected due to a circular dependency.
+        // @todo Remove this set call in https://www.drupal.org/node/2603542.
+        ->setEntityManager(\Drupal::entityManager());
+      $this->handlers['form'][$operation][$entity_type] = $form_object;
+    }
 
-    return $form_object
-      ->setStringTranslation($this->stringTranslation)
-      ->setModuleHandler($this->moduleHandler)
-      ->setEntityTypeManager($this)
-      ->setOperation($operation)
-      // The entity manager cannot be injected due to a circular dependency.
-      // @todo Remove this set call in https://www.drupal.org/node/2603542.
-      ->setEntityManager(\Drupal::entityManager());
+    return $this->handlers['form'][$operation][$entity_type];
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php b/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php
index 557f2d9..fd046a1 100644
--- a/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php
+++ b/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php
@@ -140,7 +140,10 @@ public function checkNodeAccess(array $tree) {
       $nids = array_keys($node_links);
 
       $query = $this->queryFactory->get('node');
-      $query->condition('nid', $nids, 'IN');
+      $group = $query->orConditionGroup()
+        ->condition('nid', $nids, 'IN')
+        ->condition('uuid', $nids, 'IN');
+      $query->condition($group);
 
       // Allows admins to view all nodes, by both disabling node_access
       // query rewrite as well as not checking for the node status. The
@@ -156,9 +159,11 @@ public function checkNodeAccess(array $tree) {
       }
 
       $nids = $query->execute();
-      foreach ($nids as $nid) {
-        foreach ($node_links[$nid] as $key => $link) {
-          $node_links[$nid][$key]->access = $access_result;
+      foreach ($node_links as $nid => $links) {
+        foreach ($links as $key => $link) {
+          if (isset($nids[$nid])) {
+            $node_links[$nid][$key]->access = $access_result;
+          }
         }
       }
     }
@@ -179,8 +184,8 @@ public function checkNodeAccess(array $tree) {
    */
   protected function collectNodeLinks(array &$tree, array &$node_links) {
     foreach ($tree as $key => &$element) {
-      if ($element->link->getRouteName() == 'entity.node.canonical') {
-        $nid = $element->link->getRouteParameters()['node'];
+      if (($url = $element->link->getUrlObject()) && !$url->isExternal() && $url->getRouteName() == 'entity.node.canonical') {
+        $nid = $element->link->getUrlObject()->getRouteParameters()['node'];
         $node_links[$nid][$key] = $element;
         // Deny access by default. checkNodeAccess() will re-add it.
         $element->access = AccessResult::neutral();
diff --git a/core/lib/Drupal/Core/ParamConverter/EntityConverter.php b/core/lib/Drupal/Core/ParamConverter/EntityConverter.php
index e1aa189..b8d584d 100644
--- a/core/lib/Drupal/Core/ParamConverter/EntityConverter.php
+++ b/core/lib/Drupal/Core/ParamConverter/EntityConverter.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\ParamConverter;
 
+use Drupal\Component\Uuid\Uuid;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\TypedData\TranslatableInterface;
@@ -67,6 +68,12 @@ public function convert($value, $definition, $name, array $defaults) {
     $entity_type_id = $this->getEntityTypeFromDefaults($definition, $name, $defaults);
     if ($storage = $this->entityManager->getStorage($entity_type_id)) {
       $entity = $storage->load($value);
+      // If there is no entity loadable by ID, try to load by UUID.
+      if (!$entity && Uuid::isValid($value)) {
+        if ($entities = $storage->loadByProperties(['uuid' => $value])) {
+          $entity = reset($entities);
+        }
+      }
       // If the entity type is translatable, ensure we return the proper
       // translation object for the current context.
       if ($entity instanceof EntityInterface && $entity instanceof TranslatableInterface) {
diff --git a/core/lib/Drupal/Core/RouteProcessor/RouteProcessorEntityUUID.php b/core/lib/Drupal/Core/RouteProcessor/RouteProcessorEntityUUID.php
new file mode 100644
index 0000000..3c5ef78
--- /dev/null
+++ b/core/lib/Drupal/Core/RouteProcessor/RouteProcessorEntityUUID.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\RouteProcessor\RouteProcessorEntityUUID.
+ */
+
+namespace Drupal\Core\RouteProcessor;
+
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Render\BubbleableMetadata;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Rewrites the generated URLs to entities with UUIDs to IDs.
+ */
+class RouteProcessorEntityUUID implements OutboundRouteProcessorInterface {
+
+  /**
+   * The entity manager.
+   *
+   * @var \Drupal\Core\Entity\EntityManagerInterface
+   */
+  protected $entityManager;
+
+  /**
+   * Constructs a new RouteProcessorEntityUUID instance.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager.
+   */
+  public function __construct(EntityManagerInterface $entity_manager) {
+    $this->entityManager = $entity_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function processOutbound($route_name, Route $route, array &$parameters, BubbleableMetadata $bubbleable_metadata = NULL) {
+    if (strpos($route_name, 'entity.') === 0 && list(, $entity_type, $operation) = explode('.', $route_name)) {
+      if (isset($parameters[$entity_type]) && strlen($parameters[$entity_type]) === 32) {
+        if ($entities = $this->entityManager->getStorage($entity_type)->loadByProperties(['uuid' => $parameters[$entity_type]])) {
+          /** @var \Drupal\Core\Entity\EntityInterface $entity */
+          $entity = reset($entities);
+          $parameters[$entity_type] = $entity->id();
+        }
+      }
+    }
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index 3498991..e2a89a9 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -40,8 +40,7 @@ class Registry implements DestructableInterface {
    * The complete theme registry.
    *
    * @var array
-   *   An array of theme registries, keyed by the theme name. Each registry is
-   *   an associative array keyed by theme hook names, whose values are
+   *   An associative array keyed by theme hook names, whose values are
    *   associative arrays containing the aggregated hook definition:
    *   - type: The type of the extension the original theme hook originates
    *     from; e.g., 'module' for theme hook 'node' of Node module.
@@ -80,7 +79,7 @@ class Registry implements DestructableInterface {
    *   - process: An array of theme variable process callbacks to invoke
    *     before invoking the actual theme function or template.
    */
-  protected $registry = [];
+  protected $registry;
 
   /**
    * The cache backend to use for the complete theme registry data.
@@ -97,11 +96,11 @@ class Registry implements DestructableInterface {
   protected $moduleHandler;
 
   /**
-   * An array of incomplete, runtime theme registries, keyed by theme name.
+   * The incomplete, runtime theme registry.
    *
-   * @var \Drupal\Core\Utility\ThemeRegistry[]
+   * @var \Drupal\Core\Utility\ThemeRegistry
    */
-  protected $runtimeRegistry = [];
+  protected $runtimeRegistry;
 
   /**
    * Stores whether the registry was already initialized.
@@ -210,20 +209,20 @@ protected function init($theme_name = NULL) {
    */
   public function get() {
     $this->init($this->themeName);
-    if (isset($this->registry[$this->theme->getName()])) {
-      return $this->registry[$this->theme->getName()];
+    if (isset($this->registry)) {
+      return $this->registry;
     }
     if ($cache = $this->cache->get('theme_registry:' . $this->theme->getName())) {
-      $this->registry[$this->theme->getName()] = $cache->data;
+      $this->registry = $cache->data;
     }
     else {
-      $this->build();
+      $this->registry = $this->build();
       // Only persist it if all modules are loaded to ensure it is complete.
       if ($this->moduleHandler->isLoaded()) {
         $this->setCache();
       }
     }
-    return $this->registry[$this->theme->getName()];
+    return $this->registry;
   }
 
   /**
@@ -236,17 +235,17 @@ public function get() {
    */
   public function getRuntime() {
     $this->init($this->themeName);
-    if (!isset($this->runtimeRegistry[$this->theme->getName()])) {
-      $this->runtimeRegistry[$this->theme->getName()] = new ThemeRegistry('theme_registry:runtime:' . $this->theme->getName(), $this->cache, $this->lock, array('theme_registry'), $this->moduleHandler->isLoaded());
+    if (!isset($this->runtimeRegistry)) {
+      $this->runtimeRegistry = new ThemeRegistry('theme_registry:runtime:' . $this->theme->getName(), $this->cache, $this->lock, array('theme_registry'), $this->moduleHandler->isLoaded());
     }
-    return $this->runtimeRegistry[$this->theme->getName()];
+    return $this->runtimeRegistry;
   }
 
   /**
    * Persists the theme registry in the cache backend.
    */
   protected function setCache() {
-    $this->cache->set('theme_registry:' . $this->theme->getName(), $this->registry[$this->theme->getName()], Cache::PERMANENT, array('theme_registry'));
+    $this->cache->set('theme_registry:' . $this->theme->getName(), $this->registry, Cache::PERMANENT, array('theme_registry'));
   }
 
   /**
@@ -360,9 +359,9 @@ protected function build() {
         unset($cache[$hook]['preprocess functions']);
       }
     }
-    $this->registry[$this->theme->getName()] = $cache;
+    $this->registry = $cache;
 
-    return $this->registry[$this->theme->getName()];
+    return $this->registry;
   }
 
   /**
@@ -720,12 +719,12 @@ protected function postProcessExtension(array &$cache, ActiveTheme $theme) {
    */
   public function reset() {
     // Reset the runtime registry.
-    foreach ($this->runtimeRegistry as $runtime_registry) {
-      $runtime_registry->clear();
+    if (isset($this->runtimeRegistry) && $this->runtimeRegistry instanceof ThemeRegistry) {
+      $this->runtimeRegistry->clear();
     }
-    $this->runtimeRegistry = [];
+    $this->runtimeRegistry = NULL;
 
-    $this->registry = [];
+    $this->registry = NULL;
     Cache::invalidateTags(array('theme_registry'));
     return $this;
   }
@@ -734,8 +733,8 @@ public function reset() {
    * {@inheritdoc}
    */
   public function destruct() {
-    foreach ($this->runtimeRegistry as $runtime_registry) {
-      $runtime_registry->destruct();
+    if (isset($this->runtimeRegistry)) {
+      $this->runtimeRegistry->destruct();
     }
   }
 
diff --git a/core/modules/menu_ui/menu_ui.module b/core/modules/menu_ui/menu_ui.module
index 7c01f6f..2c78f7b 100644
--- a/core/modules/menu_ui/menu_ui.module
+++ b/core/modules/menu_ui/menu_ui.module
@@ -194,8 +194,12 @@ function menu_ui_get_menu_link_defaults(NodeInterface $node) {
     // Give priority to the default menu
     $type_menus = $node_type->getThirdPartySetting('menu_ui', 'available_menus', array('main'));
     if (in_array($menu_name, $type_menus)) {
-      $query = \Drupal::entityQuery('menu_link_content')
-        ->condition('link.uri', 'node/' . $node->id())
+      $query = \Drupal::entityQuery('menu_link_content');
+      $group = $query->orConditionGroup()
+        ->condition('link.uri', 'entity:node/' . $node->id())
+        ->condition('link.uri', 'internal:/node/' . $node->id())
+        ->condition('link.uri', 'internal:/node/' . $node->uuid());
+      $query->condition($group)
         ->condition('menu_name', $menu_name)
         ->sort('id', 'ASC')
         ->range(0, 1);
@@ -205,8 +209,12 @@ function menu_ui_get_menu_link_defaults(NodeInterface $node) {
     }
     // Check all allowed menus if a link does not exist in the default menu.
     if (!$id && !empty($type_menus)) {
-      $query = \Drupal::entityQuery('menu_link_content')
+      $query = \Drupal::entityQuery('menu_link_content');
+      $group = $query->orConditionGroup()
         ->condition('link.uri', 'entity:node/' . $node->id())
+        ->condition('link.uri', 'internal:/node/' . $node->id())
+        ->condition('link.uri', 'internal:/node/' . $node->uuid());
+      $query->condition($group)
         ->condition('menu_name', array_values($type_menus), 'IN')
         ->sort('id', 'ASC')
         ->range(0, 1);
diff --git a/core/modules/menu_ui/src/Tests/MenuTest.php b/core/modules/menu_ui/src/Tests/MenuTest.php
index d88911a..53ee016 100644
--- a/core/modules/menu_ui/src/Tests/MenuTest.php
+++ b/core/modules/menu_ui/src/Tests/MenuTest.php
@@ -13,6 +13,7 @@
 use Drupal\Core\Menu\MenuLinkInterface;
 use Drupal\Core\Url;
 use Drupal\menu_link_content\Entity\MenuLinkContent;
+use Drupal\node\Entity\NodeType;
 use Drupal\system\Entity\Menu;
 use Drupal\node\Entity\Node;
 
@@ -74,7 +75,7 @@ protected function setUp() {
     $this->drupalCreateContentType(array('type' => 'article', 'name' => 'Article'));
 
     // Create users.
-    $this->adminUser = $this->drupalCreateUser(array('access administration pages', 'administer blocks', 'administer menu', 'create article content'));
+    $this->adminUser = $this->drupalCreateUser(array('access administration pages', 'administer blocks', 'administer menu', 'create article content', 'edit any article content'));
     $this->authenticatedUser = $this->drupalCreateUser(array());
   }
 
@@ -226,6 +227,14 @@ function addCustomMenu() {
     // Enable the block.
     $block = $this->drupalPlaceBlock('system_menu_block:' . $menu_name);
     $this->blockPlacements[$menu_name] = $block->id();
+
+    // Make this menu available for node-edit forms.
+    /* @var \Drupal\node\NodeTypeInterface $type */
+    $type = NodeType::load('article');
+    $node_menus = $type->getThirdPartySetting('menu_ui', 'available_menus', array('main'));
+    $node_menus[] = $menu_name;
+    $type->setThirdPartySetting('menu_ui', 'available_menus', $node_menus);
+    $type->save();
     return Menu::load($menu_name);
   }
 
@@ -471,6 +480,18 @@ function doMenuTests() {
     // Save menu links for later tests.
     $this->items[] = $item1;
     $this->items[] = $item2;
+
+    // Test links using node/{uuid}.
+    $node6 = $this->drupalCreateNode(array('type' => 'article'));
+    $uuid_link = $this->addMenuLink('', '/node/' . $node6->uuid(), $menu_name);
+    $this->verifyMenuLink($uuid_link, $node6);
+    $this->drupalGet($node6->url('edit-form'));
+    $this->assertFieldByName('menu[title]', $uuid_link->label());
+    $this->drupalPostForm(NULL, [], t('Save'));
+    \Drupal::entityManager()->getStorage('menu_link_content')->resetCache([$uuid_link->id()]);
+    /** @var \Drupal\menu_link_content\MenuLinkContentInterface $uuid_link */
+    $uuid_link = MenuLinkContent::load($uuid_link->id());
+    $this->assertEqual($uuid_link->getUrlObject(), Url::fromUri('internal:/node/' . $node6->uuid()));
   }
 
   /**
diff --git a/core/modules/system/tests/themes/test_stable/test_stable.theme b/core/modules/system/tests/themes/test_stable/test_stable.theme
deleted file mode 100644
index 8498d89..0000000
--- a/core/modules/system/tests/themes/test_stable/test_stable.theme
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-/**
- * @file
- * Test preprocess functions for theme test_stable.
- */
-
-/**
- * Implements hook_preprocess_theme_test_render_element().
- */
-function test_stable_preprocess_theme_test_render_element($variables) {
-  // This is used for Drupal\Tests\Core\Theme\RegistryTest.
-}
diff --git a/core/tests/Drupal/Tests/Core/ParamConverter/EntityConverterTest.php b/core/tests/Drupal/Tests/Core/ParamConverter/EntityConverterTest.php
index 36919a6..1365864 100644
--- a/core/tests/Drupal/Tests/Core/ParamConverter/EntityConverterTest.php
+++ b/core/tests/Drupal/Tests/Core/ParamConverter/EntityConverterTest.php
@@ -93,6 +93,12 @@ public function testConvert($value, array $definition, array $defaults, $expecte
         ['valid_id', (object) ['id' => 'valid_id']],
         ['invalid_id', NULL],
       ]);
+    $entity_storage->expects($this->any())
+      ->method('loadByProperties')
+      ->willReturnMap([
+        [['uuid' => 'invalid_id'], NULL],
+        [['uuid' => $value], [(object) ['uuid' => $value, 'id' => 'valid_id']]],
+      ]);
 
     $this->assertEquals($expected_result, $this->entityConverter->convert($value, $definition, 'foo', $defaults));
   }
@@ -108,6 +114,8 @@ public function providerTestConvert() {
     $data[] = ['invalid_id', ['type' => 'entity:entity_test'], ['foo' => 'invalid_id'], NULL];
     // Entity type placeholder.
     $data[] = ['valid_id', ['type' => 'entity:{entity_type}'], ['foo' => 'valid_id', 'entity_type' => 'entity_test'], (object) ['id' => 'valid_id']];
+    // UUID.
+    $data[] = ['1c5217f4-553c-40d8-8389-a3cc3529d79c', ['type' => 'entity:entity_test'], ['foo' => '1c5217f4-553c-40d8-8389-a3cc3529d79c'], (object) ['uuid' => '1c5217f4-553c-40d8-8389-a3cc3529d79c', 'id' => 'valid_id']];
 
     return $data;
   }
diff --git a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
index 1243118..e0c20cd 100644
--- a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
@@ -86,7 +86,8 @@ protected function setUp() {
    * Tests getting the theme registry defined by a module.
    */
   public function testGetRegistryForModule() {
-    $test_theme = new ActiveTheme([
+    $this->setupTheme('test_theme');
+    $this->registry->setTheme(new ActiveTheme([
       'name' => 'test_theme',
       'path' => 'core/modules/system/tests/themes/test_theme/test_theme.info.yml',
       'engine' => 'twig',
@@ -97,29 +98,11 @@ public function testGetRegistryForModule() {
       'libraries' => [],
       'extension' => '.twig',
       'base_themes' => [],
-    ]);
+    ]));
 
-    $test_stable = new ActiveTheme([
-      'name' => 'test_stable',
-      'path' => 'core/modules/system/tests/themes/test_stable/test_stable.info.yml',
-      'engine' => 'twig',
-      'owner' => 'twig',
-      'stylesheets_remove' => [],
-      'libraries_override' => [],
-      'libraries_extend' => [],
-      'libraries' => [],
-      'extension' => '.twig',
-      'base_themes' => [],
-    ]);
-
-    $this->themeManager->expects($this->exactly(2))
-      ->method('getActiveTheme')
-      ->willReturnOnConsecutiveCalls($test_theme, $test_stable);
-
-    // Include the module and theme files so that hook_theme can be called.
+    // Include the module so that hook_theme can be called.
     include_once $this->root . '/core/modules/system/tests/modules/theme_test/theme_test.module';
-    include_once $this->root . '/core/modules/system/tests/themes/test_stable/test_stable.theme';
-    $this->moduleHandler->expects($this->exactly(2))
+    $this->moduleHandler->expects($this->once())
       ->method('getImplementations')
       ->with('theme')
       ->will($this->returnValue(array('theme_test')));
@@ -143,24 +126,16 @@ public function testGetRegistryForModule() {
     $this->assertArrayHasKey('theme_test_function_template_override', $registry);
 
     $this->assertArrayNotHasKey('test_theme_not_existing_function', $registry);
-    $this->assertFalse(in_array('test_stable_preprocess_theme_test_render_element', $registry['theme_test_render_element']['preprocess functions']));
 
     $info = $registry['theme_test_function_suggestions'];
     $this->assertEquals('module', $info['type']);
     $this->assertEquals('core/modules/system/tests/modules/theme_test', $info['theme path']);
     $this->assertEquals('theme_theme_test_function_suggestions', $info['function']);
     $this->assertEquals(array(), $info['variables']);
-
-    // The second call will initialize with the second theme. Ensure that this
-    // returns a different object and the discovery for the second theme's
-    // preprocess function worked.
-    $other_registry = $this->registry->get();
-    $this->assertNotSame($registry, $other_registry);
-    $this->assertTrue(in_array('test_stable_preprocess_theme_test_render_element', $other_registry['theme_test_render_element']['preprocess functions']));
   }
 
-  protected function setupTheme() {
-    $this->registry = new TestRegistry($this->root, $this->cache, $this->lock, $this->moduleHandler, $this->themeHandler, $this->themeInitialization);
+  protected function setupTheme($theme_name = NULL) {
+    $this->registry = new TestRegistry($this->root, $this->cache, $this->lock, $this->moduleHandler, $this->themeHandler, $this->themeInitialization, $theme_name);
     $this->registry->setThemeManager($this->themeManager);
   }
 
@@ -168,10 +143,23 @@ protected function setupTheme() {
 
 class TestRegistry extends Registry {
 
+  public function setTheme(ActiveTheme $theme) {
+    $this->theme = $theme;
+  }
+
+  protected function init($theme_name = NULL) {
+  }
+
   protected function getPath($module) {
     if ($module == 'theme_test') {
       return 'core/modules/system/tests/modules/theme_test';
     }
   }
 
+  protected function listThemes() {
+  }
+
+  protected function initializeTheme() {
+  }
+
 }