diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 43d7368..bd5f693 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -695,7 +695,7 @@ function watchdog_exception($type, Exception $exception, $message = NULL, $varia
  *   If there are no messages set, the function returns NULL.
  *
  * @see drupal_get_messages()
- * @see theme_status_messages()
+ * @see status-messages.html.twig
  */
 function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE) {
   if (isset($message)) {
@@ -742,7 +742,7 @@ function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE) 
  *   drupal_set_message() for the array structure of individual messages.
  *
  * @see drupal_set_message()
- * @see theme_status_messages()
+ * @see status-messages.html.twig
  */
 function drupal_get_messages($type = NULL, $clear_queue = TRUE) {
   if ($messages = drupal_set_message()) {
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 001c9e7..df4e298 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -2063,8 +2063,8 @@ function _drupal_add_library($library_name, $every_page = NULL) {
  *
  * To set up a table to use drag and drop in place of weight select-lists or in
  * place of a form that contains parent relationships, the form must be themed
- * into a table. The table must have an ID attribute set. If using
- * theme_table(), the ID may be set as follows:
+ * into a table. The table must have an ID attribute set and it
+ * may be set as follows:
  * @code
  * $table = array(
  *   '#type' => 'table',
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 0bffd39..87d5ea8 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -548,7 +548,7 @@ function template_preprocess_form_element(&$variables) {
  *
  * Form element labels include the #title and a #required marker. The label is
  * associated with the element itself by the element #id. Labels may appear
- * before or after elements, depending on theme_form_element() and
+ * before or after elements, depending on form-element.html.twig and
  * #title_display.
  *
  * This function will not be called for elements with no labels, depending on
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index d094c17..459a1de 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1418,9 +1418,9 @@ function template_preprocess_item_list(&$variables) {
         // If this child element does not specify how it can be rendered, then
         // we need to inherit the render properties of the current list.
         if (!isset($child['#type']) && !isset($child['#theme']) && !isset($child['#markup'])) {
-          // Since theme_item_list() supports both strings and render arrays as
-          // items, the items of the nested list may have been specified as the
-          // child elements of the nested list, instead of #items. For
+          // Since item-list.html.twig supports both strings and render arrays
+          // as items, the items of the nested list may have been specified as
+          // the child elements of the nested list, instead of #items. For
           // convenience, we automatically move them into #items.
           if (!isset($child['#items'])) {
             // This is the same condition as in
@@ -1876,7 +1876,7 @@ function theme_get_suggestions($args, $base, $delimiter = '__') {
 }
 
 /**
- * Prepare variables for maintenance page templates.
+ * Prepares variables for maintenance page templates.
  *
  * Default template: maintenance-page.html.twig.
  *
diff --git a/core/lib/Drupal/Core/Database/Query/TableSortExtender.php b/core/lib/Drupal/Core/Database/Query/TableSortExtender.php
index 4786f59..56cfc2c 100644
--- a/core/lib/Drupal/Core/Database/Query/TableSortExtender.php
+++ b/core/lib/Drupal/Core/Database/Query/TableSortExtender.php
@@ -37,7 +37,7 @@ class TableSortExtender extends SelectExtender {
    * @return \Drupal\Core\Database\Query\SelectInterface
    *   The called object.
    *
-   * @see theme_table()
+   * @see table.html.twig
    */
   public function orderByHeader(array $header) {
     $this->header = $header;
diff --git a/core/lib/Drupal/Core/Entity/EntityListBuilder.php b/core/lib/Drupal/Core/Entity/EntityListBuilder.php
index 9e41b08..aac3763 100644
--- a/core/lib/Drupal/Core/Entity/EntityListBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityListBuilder.php
@@ -184,7 +184,7 @@ class EntityListBuilder extends EntityHandlerBase implements EntityListBuilderIn
   /**
    * {@inheritdoc}
    *
-   * Builds the entity listing as renderable array for theme_table().
+   * Builds the entity listing as renderable array for table.html.twig.
    *
    * @todo Add a link to add a new item to the #empty text.
    */
diff --git a/core/lib/Drupal/Core/Entity/Query/QueryInterface.php b/core/lib/Drupal/Core/Entity/Query/QueryInterface.php
index 5a34cac..c617204 100644
--- a/core/lib/Drupal/Core/Entity/Query/QueryInterface.php
+++ b/core/lib/Drupal/Core/Entity/Query/QueryInterface.php
@@ -149,7 +149,7 @@
    * Enables sortable tables for this query.
    *
    * @param $headers
-   *   An array of headers of the same structure as described in theme_table().
+   *   An array of headers of the same structure as described in table.html.twig.
    *   Use a 'specifier' in place of a 'field' to specify what to sort on.
    *   This can be an entity or a field as described in condition().
    * @return \Drupal\Core\Entity\Query\QueryInterface
diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index d204050..ecb7c24 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -614,9 +614,9 @@ class FormBuilder implements FormBuilderInterface, FormValidatorInterface, FormS
 
     $build_info = $form_state->getBuildInfo();
     // If no #theme has been set, automatically apply theme suggestions.
-    // theme_form() itself is in #theme_wrappers and not #theme. Therefore, the
-    // #theme function only has to care for rendering the inner form elements,
-    // not the form itself.
+    // form.html.twig itself is in #theme_wrappers and not #theme. Therefore,
+    // the #theme function only has to care for rendering the inner form
+    // elements, not the form itself.
     if (!isset($form['#theme'])) {
       $form['#theme'] = array($form_id);
       if (isset($build_info['base_form_id'])) {
diff --git a/core/lib/Drupal/Core/Render/Element/Table.php b/core/lib/Drupal/Core/Render/Element/Table.php
index 08c539a..39db4e4 100644
--- a/core/lib/Drupal/Core/Render/Element/Table.php
+++ b/core/lib/Drupal/Core/Render/Element/Table.php
@@ -234,10 +234,11 @@ class Table extends FormElement {
   }
 
   /**
-   * #pre_render callback to transform children of an element into #rows suitable for theme_table().
+   * #pre_render callback to transform children of an element into #rows
+   * suitable for table.html.twig.
    *
    * This function converts sub-elements of an element of #type 'table' to be
-   * suitable for theme_table():
+   * suitable for table.html.twig:
    * - The first level of sub-elements are table rows. Only the #attributes
    *   property is taken into account.
    * - The second level of sub-elements is converted into columns for the
@@ -294,7 +295,7 @@ class Table extends FormElement {
    *
    * @return array
    *
-   * @see theme_table()
+   * @see template_preprocess_table()
    * @see drupal_process_attached()
    * @see drupal_attach_tabledrag()
    */
diff --git a/core/lib/Drupal/Core/Render/Element/Tableselect.php b/core/lib/Drupal/Core/Render/Element/Tableselect.php
index 0833369..0fa833a 100644
--- a/core/lib/Drupal/Core/Render/Element/Tableselect.php
+++ b/core/lib/Drupal/Core/Render/Element/Tableselect.php
@@ -132,7 +132,7 @@ class Tableselect extends Table {
         // Render the checkbox / radio element.
         $row['data'][] = drupal_render($element[$key]);
 
-        // As theme_table only maps header and row columns by order, create the
+        // As table.html.twig only maps header and row columns by order, create the
         // correct order by iterating over the header fields.
         foreach ($element['#header'] as $fieldname => $title) {
           // A row cell can span over multiple headers, which means less row cells
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
index 474c654..854d3ce 100644
--- a/core/modules/block/templates/block-list.html.twig
+++ b/core/modules/block/templates/block-list.html.twig
@@ -5,7 +5,7 @@
  *
  * This template will be used when a block edit form specifies 'block_edit_form'
  * as its #theme callback.  Otherwise, by default, block add/edit forms will be
- * themed by theme_form().
+ * themed by form.html.twig.
  *
  * Available variables:
  * - form: The block add/edit form.
diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index 7f7830c..6b1d38a 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -501,7 +501,7 @@ function template_preprocess_book_node_export_html(&$variables) {
 }
 
 /**
- * Implements template_preprocess_HOOK() for theme_book_tree().
+ * Implements template_preprocess_HOOK() for book-tree.html.twig.
  */
 function template_preprocess_book_tree(&$variables) {
   $variables['tree'] = $variables['tree']['#children'];
diff --git a/core/modules/config_translation/src/Controller/ConfigTranslationMapperList.php b/core/modules/config_translation/src/Controller/ConfigTranslationMapperList.php
index 23007e9..9e5ed09 100644
--- a/core/modules/config_translation/src/Controller/ConfigTranslationMapperList.php
+++ b/core/modules/config_translation/src/Controller/ConfigTranslationMapperList.php
@@ -46,7 +46,7 @@ class ConfigTranslationMapperList extends ControllerBase {
   }
 
   /**
-   * Builds the mappers as a renderable array for theme_table().
+   * Builds the mappers as a renderable array for table.html.twig.
    *
    * @return array
    *   Renderable array with config translation mappers.
diff --git a/core/modules/node/templates/node-edit-form.html.twig b/core/modules/node/templates/node-edit-form.html.twig
index e34baf9..6d8ac2a 100644
--- a/core/modules/node/templates/node-edit-form.html.twig
+++ b/core/modules/node/templates/node-edit-form.html.twig
@@ -7,7 +7,7 @@
  *
  * This template will be used when a node edit form specifies 'node_edit_form'
  * as its #theme callback.  Otherwise, by default, node add/edit forms will be
- * themed by theme_form().
+ * themed by form.html.twig.
  *
  * Available variables:
  * - form: The node add/edit form.
diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index c3fce4f..ae06709 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -538,7 +538,7 @@ function rdf_preprocess_taxonomy_term(&$variables) {
 }
 
 /**
- * Implements hook_preprocess_HOOK() for theme_image().
+ * Implements hook_preprocess_HOOK() for image.html.twig.
  */
 function rdf_preprocess_image(&$variables) {
   // Adds the RDF type for image.  We cannot use the usual entity-based mapping
diff --git a/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
index 48fc3dd..338866b 100644
--- a/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -11,7 +11,7 @@
 }
 
 /**
- * Markup generated by theme_tablesort_indicator().
+ * Markup generated by tablesort-indicator.html.twig.
  */
 th.active img {
   display: inline;
@@ -21,7 +21,7 @@ td.active {
 }
 
 /**
- * Markup generated by theme_item_list().
+ * Markup generated by item-list.html.twig.
  */
 .item-list .title {
   font-weight: bold;
@@ -398,7 +398,7 @@ ul.links a.active {
 }
 
 /**
- * Markup generated by theme_breadcrumb().
+ * Markup generated by breadcrumb.html.twig.
  */
 .breadcrumb {
   padding-bottom: 0.5em;
diff --git a/core/modules/system/src/SystemManager.php b/core/modules/system/src/SystemManager.php
index 145705f..0107453 100644
--- a/core/modules/system/src/SystemManager.php
+++ b/core/modules/system/src/SystemManager.php
@@ -195,7 +195,7 @@ class SystemManager {
    *   The menu item to be displayed.
    *
    * @return array
-   *   An array of menu items, as expected by theme_admin_block_content().
+   *   An array of menu items, as expected by admin-block-content.html.twig.
    */
   public function getAdminBlock(MenuLinkInterface $instance) {
     $content = array();
diff --git a/core/modules/system/src/Tests/Theme/FunctionsTest.php b/core/modules/system/src/Tests/Theme/FunctionsTest.php
index f9a4a83..c1ad1c7 100644
--- a/core/modules/system/src/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/src/Tests/Theme/FunctionsTest.php
@@ -28,7 +28,7 @@ class FunctionsTest extends WebTestBase {
   public static $modules = array('router_test');
 
   /**
-   * Tests theme_item_list().
+   * Tests item-list.html.twig.
    */
   function testItemList() {
     // Verify that empty items produce no output.
diff --git a/core/modules/views/src/Plugin/views/PluginBase.php b/core/modules/views/src/Plugin/views/PluginBase.php
index 7992378..5268405 100644
--- a/core/modules/views/src/Plugin/views/PluginBase.php
+++ b/core/modules/views/src/Plugin/views/PluginBase.php
@@ -29,9 +29,8 @@
  *   template engine extension).
  *   If a template file should be used, the file has to be placed in the
  *   module's templates folder.
- *   Example: theme = "mymodule_row" of module "mymodule" will implement either
- *   theme_mymodule_row() or mymodule-row.html.twig in the
- *   [..]/modules/mymodule/templates folder.
+ *   Example: theme = "mymodule_row" of module "mymodule" will implement
+ *   mymodule-row.html.twig in the [..]/modules/mymodule/templates folder.
  * - register_theme: (optional) When set to TRUE (default) the theme is
  *   registered automatically. When set to FALSE the plugin reuses an existing
  *   theme implementation, defined by another module or views plugin.
diff --git a/core/modules/views/views.api.php b/core/modules/views/views.api.php
index a537fe6..a0d27ca 100644
--- a/core/modules/views/views.api.php
+++ b/core/modules/views/views.api.php
@@ -832,7 +832,7 @@ function hook_views_query_alter(ViewExecutable $view, QueryPluginBase $query) {
  *   The view object.
  *
  * @see \Drupal\views_ui\ViewUI
- * @see theme_table()
+ * @see table.html.twig
  */
 function hook_views_preview_info_alter(array &$rows, ViewExecutable $view) {
   // Adds information about the tables being queried by the view to the query