diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index 61212febe21d..0360b6ec5f28 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -6,12 +6,12 @@
  */
 
 /**
- * Implements hook_preprocess_HOOK() for maintenance-page.tpl.php.
+ * Implements hook_preprocess_HOOK() for maintenance-page.html.twig.
  */
 function seven_preprocess_maintenance_page(&$vars) {
   // While markup for normal pages is split into page.tpl.php and html.tpl.php,
   // the markup for the maintenance page is all in the single
-  // maintenance-page.tpl.php template. So, to have what's done in
+  // maintenance-page.html.twig template. So, to have what's done in
   // seven_preprocess_html() also happen on the maintenance page, it has to be
   // called here.
   seven_preprocess_html($vars);
diff --git a/core/themes/seven/templates/maintenance-page.html.twig b/core/themes/seven/templates/maintenance-page.html.twig
new file mode 100644
index 000000000000..02af912884d5
--- /dev/null
+++ b/core/themes/seven/templates/maintenance-page.html.twig
@@ -0,0 +1,57 @@
+{#
+/**
+ * @file
+ * Seven's theme implementation to display a single Drupal page while offline.
+ *
+ * All of the available variables are mirrored in page.html.twig.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_maintenance_page()
+ * @see seven_preprocess_maintenance_page()
+ *
+ * @ingroup themeable
+ */
+#}
+<!DOCTYPE html>
+<html lang="{{ language.langcode }}" dir="{{ language.dir }}">
+  <head>
+    <title>{{ head_title }}</title>
+    {{ head }}
+    {{ styles }}
+    {{ scripts }}
+  </head>
+  <body{{ attributes }}>
+
+  {{ page_top }}
+
+  <header id="branding">
+    {% if title %}<h1 class="page-title">{{ title }}</h1>{% endif %}
+  </header>
+
+  <div id="page">
+    <div id="sidebar-first" class="sidebar">
+      {% if logo %}
+        <img id="logo" src="{{ logo }}" alt="{{ site_name }}" />
+      {% endif %}
+      {{ sidebar_first }}
+    </div>
+
+    <main id="content" class="clearfix">
+      {% if messages %}
+        <div id="console">{{ messages }}</div>
+      {% endif %}
+      {% if help %}
+        <div id="help">
+          {{ help }}
+        </div>
+      {% endif %}
+      {{ content }}
+    </main>
+  </div>
+
+  <footer role="contentinfo">
+    {{ page_bottom }}
+  </footer>
+
+  </body>
+</html>
diff --git a/core/themes/seven/templates/maintenance-page.tpl.php b/core/themes/seven/templates/maintenance-page.tpl.php
deleted file mode 100644
index fff11d848a50..000000000000
--- a/core/themes/seven/templates/maintenance-page.tpl.php
+++ /dev/null
@@ -1,62 +0,0 @@
-<?php
-
-/**
- * @file
- * Seven's theme implementation to display a single Drupal page while offline.
- *
- * All of the available variables are mirrored in page.tpl.php.
- *
- * @see template_preprocess()
- * @see template_preprocess_maintenance_page()
- * @see seven_preprocess_maintenance_page()
- *
- * @ingroup themeable
- */
-?>
-<!DOCTYPE html>
-<html lang="<?php print $language->langcode ?>" dir="<?php print $language->dir ?>">
-  <head>
-    <title><?php print $head_title; ?></title>
-    <?php print $head; ?>
-    <?php print $styles; ?>
-    <?php print $scripts; ?>
-  </head>
-  <body class="<?php print $attributes['class']; ?>">
-
-  <?php print $page_top; ?>
-
-  <header id="branding">
-    <?php if ($title): ?><h1 class="page-title"><?php print $title; ?></h1><?php endif; ?>
-  </header>
-
-  <div id="page">
-
-    <div id="sidebar-first" class="sidebar">
-      <?php if ($logo): ?>
-        <img id="logo" src="<?php print $logo ?>" alt="<?php print $site_name ?>" />
-      <?php endif; ?>
-      <?php if ($sidebar_first): ?>
-        <?php print $sidebar_first ?>
-      <?php endif; ?>
-    </div>
-
-    <main id="content" class="clearfix">
-      <?php if ($messages): ?>
-        <div id="console"><?php print $messages; ?></div>
-      <?php endif; ?>
-      <?php if ($help): ?>
-        <div id="help">
-          <?php print $help; ?>
-        </div>
-      <?php endif; ?>
-      <?php print $content; ?>
-    </main>
-
-  </div>
-
-  <footer role="contentinfo">
-    <?php print $page_bottom; ?>
-  </footer>
-
-  </body>
-</html>
