diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index 06e3cb27141d80fffbddb3f25649331403e19b98..7238278fb7c0f9342ff82a4c08e3761a03fd5db0 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -59,6 +59,7 @@ function aggregator_theme() {
     ),
     'aggregator_block_item' => array(
       'variables' => array('item' => NULL, 'feed' => 0),
+      'template' => 'aggregator-block-item',
     ),
     'aggregator_summary_items' => array(
       'variables' => array('summary_items' => NULL, 'source' => NULL),
@@ -68,6 +69,7 @@ function aggregator_theme() {
     'aggregator_summary_item' => array(
       'variables' => array('aggregator_item' => NULL, 'view_mode' => NULL),
       'file' => 'aggregator.pages.inc',
+      'template' => 'aggregator-summary-item',
     ),
     'aggregator_item' => array(
       'variables' => array('aggregator_item' => NULL, 'view_mode' => NULL),
@@ -435,18 +437,19 @@ function aggregator_category_load($cid) {
 }
 
 /**
- * Returns HTML for an individual feed item for display in the block.
+ * Prepares variables for individual feed item block templates.
  *
- * @param $variables
+ * Default template: aggregator-block-item.html.twig.
+ *
+ * @param array $variables
  *   An associative array containing:
  *   - item: The item to be displayed.
  *   - feed: Not used.
- *
- * @ingroup themeable
  */
-function theme_aggregator_block_item($variables) {
+function template_preprocess_aggregator_block_item(&$variables) {
   // Display the external link to the item.
-  return '<a href="' . check_url($variables['item']->link) . '">' . check_plain($variables['item']->title) . "</a>\n";
+  $variables['url'] = check_url($variables['item']->link);
+  $variables['title'] = check_plain($variables['item']->title);
 }
 
 /**
diff --git a/core/modules/aggregator/aggregator.pages.inc b/core/modules/aggregator/aggregator.pages.inc
index cd938e7a816bfa7405bbc93e644916a34d6fe90c..a711c18ae12ccfb22ab356b676f240c5c2197bac 100644
--- a/core/modules/aggregator/aggregator.pages.inc
+++ b/core/modules/aggregator/aggregator.pages.inc
@@ -50,21 +50,6 @@ function aggregator_load_feed_items($type, $data = NULL, $limit = 20) {
   }
 }
 
-/**
- * Default theme implementation to present a linked feed item for summaries.
- *
- * @param $variables
- *   An associative array containing:
- *   - item_link: Link to item.
- *   - item_age: Age of the item.
- *
- * @see template_preprocess()
- * @see template_preprocess_aggregator_summary_item()
- */
-function theme_aggregator_summary_item($variables) {
-  return $variables['item_url'] . ' ' . $variables['item_age'];
-}
-
 /**
  * Prepares variables for aggregator item templates.
  *
@@ -200,21 +185,20 @@ function template_preprocess_aggregator_summary_items(&$variables) {
 function template_preprocess_aggregator_summary_item(&$variables) {
   $item = $variables['aggregator_item'];
 
-  $variables['item_url'] = l(check_plain($item->label()), check_url(url($item->link->value, array('absolute' => TRUE))), array(
+  $variables['url'] = l(check_plain($item->label()), check_url(url($item->link->value, array('absolute' => TRUE))), array(
     'attributes' => array(
       'class' => array('feed-item-url',),
     ),
   ));
-  $datetime = array(
+  $variables['age'] = array(
     '#theme' => 'datetime',
     '#attributes' => array(
       'datetime' => format_date($item->timestamp->value, 'html_datetime', '', 'UTC'),
-      'class' => array('feed-item-age',),
+      'class' => array('feed-item-age'),
     ),
     '#text' => t('%age old', array('%age' => format_interval(REQUEST_TIME - $item->timestamp->value))),
     '#html' => TRUE,
   );
-  $variables['item_age'] = drupal_render($datetime);
 }
 
 /**
diff --git a/core/modules/aggregator/templates/aggregator-block-item.html.twig b/core/modules/aggregator/templates/aggregator-block-item.html.twig
new file mode 100644
index 0000000000000000000000000000000000000000..c5a7f3c155e083fa1c3d8214f2f1be90831f2f78
--- /dev/null
+++ b/core/modules/aggregator/templates/aggregator-block-item.html.twig
@@ -0,0 +1,15 @@
+{#
+/**
+ * @file
+ * Default theme implementation for feed item for display in the block.
+ *
+ * Available variables:
+ * - url: URL to the feed item.
+ * - title: Title of the feed item.
+ *
+ * @see template_preprocess_aggregator_block_item()
+ *
+ * @ingroup themeable
+ */
+#}
+<a href="{{ url }}">{{ title }}</a>
diff --git a/core/modules/aggregator/templates/aggregator-summary-item.html.twig b/core/modules/aggregator/templates/aggregator-summary-item.html.twig
new file mode 100644
index 0000000000000000000000000000000000000000..74ad9970244c0b2f2342ccaa2acb6f63e7a8a2d2
--- /dev/null
+++ b/core/modules/aggregator/templates/aggregator-summary-item.html.twig
@@ -0,0 +1,15 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a single feed in a list of feed items.
+ *
+ * Available variables:
+ * - link: Link to item.
+ * - age: Age of the item.
+ *
+ * @see template_preprocess_aggregator_summary_item()
+ *
+ * @ingroup themeable
+ */
+#}
+{{ url }} {{ age }}