diff --git a/core/core.services.yml b/core/core.services.yml
index c26834c..551d881 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -948,8 +948,8 @@ services:
   twig.loader:
     alias: twig.loader.filesystem
   twig.loader.filesystem:
-    class: Twig_Loader_Filesystem
-    arguments: ['%app.root%']
+    class: Drupal\Core\Template\TwigThemeRegistryLoader
+    arguments: ['%app.root%', '@theme.registry']
   element_info:
     alias: plugin.manager.element_info
   file.mime_type.guesser:
diff --git a/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php b/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php
new file mode 100644
index 0000000..ec6e17e
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php
@@ -0,0 +1,131 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Template\TwigThemeRegistryLoader.
+ */
+
+namespace Drupal\Core\Template;
+
+use Drupal\Core\Theme\Registry;
+
+/**
+ * Registers paths based on information from the Drupal theme registry.
+ *
+ * Allows for template inheritance based on the currently active template.
+ */
+class TwigThemeRegistryLoader extends \Twig_Loader_Filesystem {
+
+  /**
+   * The theme registry used to determine which template to use.
+   *
+   * @var \Drupal\Core\Theme\Registry
+   */
+  protected $themeRegistry;
+
+  /**
+   * Constructs a new TwigThemeRegistryLoader object.
+   *
+   * @param string|array $paths
+   *   A path or an array of paths where to look for templates
+   * @param \Drupal\Core\Theme\Registry $theme_registry
+   *   The theme registry.
+   */
+  public function __construct($paths = array(), Registry $theme_registry) {
+    if ($paths) {
+      $this->setPaths($paths);
+    }
+    $this->themeRegistry = $theme_registry;
+  }
+
+  /**
+   * Finds the path to the requested template.
+   *
+   * @param string $name
+   *   The name of the template to load.
+   *
+   * @return string
+   *   The path to the template.
+   *
+   * @throws Twig_Error_Loader
+   *   Thrown if a template matching $name cannot be found.
+   */
+  protected function findTemplate($name) {
+    // Go through the normal findTemplate() checks based on path and namespaced
+    // path.
+    if ($default = $this->findTemplateDefault($name)) {
+      return $default;
+    }
+
+    // Allow for loading based on the Drupal theme registry.
+    $hook = str_replace('.html.twig', '', strtr($name, '-', '_'));
+    $theme_registry = $this->themeRegistry->getRuntime();
+
+    if ($theme_registry->has($hook)) {
+      $info = $theme_registry->get($hook);
+      if (isset($info['path'])) {
+        $path = $info['path'] . '/' . $name;
+      }
+      elseif (isset($info['template'])) {
+        $path = $info['template'] . '.html.twig';
+      }
+      if (isset($path) && is_file($path)) {
+        return $this->cache[$name] = $path;
+      }
+    }
+
+    throw new \Twig_Error_Loader(sprintf('Unable to find template "%s" (looked into: %s).', $name, implode(', ', $this->paths[$namespace])));
+  }
+
+  /**
+   * Finds the path to the requested template using standard methods.
+   *
+   * This is copied from Twig_Loader_Filesystem::findTemplate() and allows
+   * loading based on the path or namespaced path. The final throw has been
+   * removed and is in findTemplate() instead to allow additional loading based
+   * on the Drupal theme registry.
+   *
+   * @param string $name
+   *   The name of the template to load.
+   *
+   * @return string
+   *   The path to the template if one is found.
+   *
+   * @throws Twig_Error_Loader
+   *   Thrown if namespace-related errors occur.
+   */
+  protected function findTemplateDefault($name) {
+    $name = (string) $name;
+
+    // Normalize name.
+    $name = preg_replace('#/{2,}#', '/', strtr($name, '\\', '/'));
+
+    if (isset($this->cache[$name])) {
+      return $this->cache[$name];
+    }
+
+    $this->validateName($name);
+
+    $namespace = self::MAIN_NAMESPACE;
+    $shortname = $name;
+    if (isset($name[0]) && '@' == $name[0]) {
+      if (false === $pos = strpos($name, '/')) {
+        throw new \Twig_Error_Loader(sprintf('Malformed namespaced template name "%s" (expecting "@namespace/template_name").', $name));
+      }
+
+      $namespace = substr($name, 1, $pos - 1);
+      $shortname = substr($name, $pos + 1);
+    }
+
+    if (!isset($this->paths[$namespace])) {
+      throw new \Twig_Error_Loader(sprintf('There are no registered paths for namespace "%s".', $namespace));
+    }
+
+    foreach ($this->paths[$namespace] as $path) {
+      if (is_file($path . '/' . $shortname)) {
+        return $this->cache[$name] = $path . '/' . $shortname;
+      }
+    }
+  }
+
+}
diff --git a/core/modules/system/src/Tests/Theme/TwigRegistryLoaderTest.php b/core/modules/system/src/Tests/Theme/TwigRegistryLoaderTest.php
new file mode 100644
index 0000000..e62497b
--- /dev/null
+++ b/core/modules/system/src/Tests/Theme/TwigRegistryLoaderTest.php
@@ -0,0 +1,70 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Theme\TwigRegistryLoaderTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests Twig registry loader.
+ *
+ * @group Theme
+ */
+class TwigRegistryLoaderTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('twig_theme_test', 'block');
+
+  /**
+   * @var \Drupal\Core\Template\TwigEnvironment
+   */
+  protected $twig;
+
+  protected function setUp() {
+    parent::setUp();
+    theme_enable(array('test_theme_twig_registry_loader'));
+    $this->twig = \Drupal::service('twig');
+  }
+
+  /**
+   * Checks to see if a value is a twig template.
+   */
+  public function assertTwigTemplate($value, $message = '', $group = 'Other') {
+    $this->assertTrue($value instanceof \Twig_Template, $message, $group);
+  }
+
+  /**
+   * Tests template discovery using the Drupal theme registry.
+   */
+  public function testTemplateDiscovery() {
+    $this->assertTwigTemplate($this->twig->resolveTemplate('block.html.twig'), 'Found block.html.twig in block module.');
+  }
+
+  /**
+   * Tests template extension and includes using the Drupal theme registry.
+   */
+  public function testTwigNamespaces() {
+    // Test the module-provided extend and insert templates.
+    $this->drupalGet('twig-theme-test/registry-loader');
+    $this->assertText('This line is from twig_theme_test/templates/twig_registry_loader_test_extend.html.twig');
+    $this->assertText('This line is from twig_theme_test/templates/twig_registry_loader_test_include.html.twig');
+
+    // Enable a theme that overrides the extend and insert templates to ensure
+    // they are picked up by the registry loader.
+    \Drupal::config('system.theme')
+      ->set('default', 'test_theme_twig_registry_loader')
+      ->save();
+    $this->drupalGet('twig-theme-test/registry-loader');
+    $this->assertText('This line is from test_theme_twig_registry_loader/templates/twig_registry_loader_test_extend.html.twig');
+    $this->assertText('This line is from test_theme_twig_registry_loader/templates/twig_registry_loader_test_include.html.twig');
+  }
+
+}
diff --git a/core/modules/system/templates/block--system-branding-block.html.twig b/core/modules/system/templates/block--system-branding-block.html.twig
index 4cf0f1a..f648773 100644
--- a/core/modules/system/templates/block--system-branding-block.html.twig
+++ b/core/modules/system/templates/block--system-branding-block.html.twig
@@ -1,4 +1,4 @@
-{% extends "@block/block.html.twig" %}
+{% extends "block.html.twig" %}
 {#
 /**
  * @file
diff --git a/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php b/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
index d454e5f..842a8e8 100644
--- a/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
+++ b/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
@@ -37,4 +37,11 @@ public function urlGeneratorRender() {
     );
   }
 
+  /**
+   * Menu callback for testing the Twig registry loader.
+   */
+  public function registryLoaderRender() {
+    return array('#theme' => 'twig_registry_loader_test');
+  }
+
 }
diff --git a/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test.html.twig b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test.html.twig
new file mode 100644
index 0000000..8776f5e
--- /dev/null
+++ b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test.html.twig
@@ -0,0 +1,5 @@
+{% extends "twig_registry_loader_test_extend.html.twig" %}
+
+{% block content %}
+  {% include "twig_registry_loader_test_include.html.twig" %}
+{% endblock %}
diff --git a/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_extend.html.twig b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_extend.html.twig
new file mode 100644
index 0000000..a5a5af1
--- /dev/null
+++ b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_extend.html.twig
@@ -0,0 +1,5 @@
+This line is from twig_theme_test/templates/twig_registry_loader_test_extend.html.twig
+
+{% block content %}
+This text is in a block.
+{% endblock %}
diff --git a/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_include.html.twig b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_include.html.twig
new file mode 100644
index 0000000..bb8c056
--- /dev/null
+++ b/core/modules/system/tests/modules/twig_theme_test/templates/twig_registry_loader_test_include.html.twig
@@ -0,0 +1 @@
+This line is from twig_theme_test/templates/twig_registry_loader_test_include.html.twig
diff --git a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
index 0497c7b..046e994 100644
--- a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
+++ b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
@@ -19,6 +19,18 @@ function twig_theme_test_theme($existing, $type, $theme, $path) {
     'variables' => array(),
     'template' => 'twig_namespace_test',
   );
+  $items['twig_registry_loader_test'] = array(
+    'variables' => array(),
+    'template' => 'twig_registry_loader_test',
+  );
+  $items['twig_registry_loader_test_include'] = array(
+    'variables' => array(),
+    'template' => 'twig_registry_loader_test_include',
+  );
+  $items['twig_registry_loader_test_extend'] = array(
+    'variables' => array(),
+    'template' => 'twig_registry_loader_test_extend',
+  );
   $items['twig_raw_test'] = array(
     'variables' => array('script' => ''),
     'template' => 'twig-raw-test',
diff --git a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
index 75b9bbb..77f1bf3 100644
--- a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
+++ b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
@@ -18,3 +18,10 @@ twig_theme_test_url_generator:
     _content: '\Drupal\twig_theme_test\TwigThemeTestController::urlGeneratorRender'
   requirements:
     _access: 'TRUE'
+
+twig_theme_test.registry_loader:
+  path: '/twig-theme-test/registry-loader'
+  defaults:
+    _content: '\Drupal\twig_theme_test\TwigThemeTestController::registryLoaderRender'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_extend.html.twig b/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_extend.html.twig
new file mode 100644
index 0000000..7d5cb0e
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_extend.html.twig
@@ -0,0 +1,5 @@
+This line is from test_theme_twig_registry_loader/templates/twig_registry_loader_test_extend.html.twig
+
+{% block content %}
+This text is in a block.
+{% endblock %}
diff --git a/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_include.html.twig b/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_include.html.twig
new file mode 100644
index 0000000..7097adf
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig_registry_loader/templates/twig_registry_loader_test_include.html.twig
@@ -0,0 +1 @@
+This line is from test_theme_twig_registry_loader/templates/twig_registry_loader_test_include.html.twig
diff --git a/core/modules/system/tests/themes/test_theme_twig_registry_loader/test_theme_twig_registry_loader.info.yml b/core/modules/system/tests/themes/test_theme_twig_registry_loader/test_theme_twig_registry_loader.info.yml
new file mode 100644
index 0000000..9ee01c5
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig_registry_loader/test_theme_twig_registry_loader.info.yml
@@ -0,0 +1,5 @@
+name: 'Twig registry loader test'
+type: theme
+description: 'Support module for Twig registry loader testing.'
+version: VERSION
+core: 8.x
diff --git a/core/themes/bartik/templates/block--system-branding-block.html.twig b/core/themes/bartik/templates/block--system-branding-block.html.twig
index f6147a6..4a4b733 100644
--- a/core/themes/bartik/templates/block--system-branding-block.html.twig
+++ b/core/themes/bartik/templates/block--system-branding-block.html.twig
@@ -1,4 +1,4 @@
-{% extends "@block/block.html.twig" %}
+{% extends "block.html.twig" %}
 {#
 /**
  * @file