diff --git a/core/modules/system/src/Tests/Common/PageRenderTest.php b/core/modules/system/src/Tests/Common/PageRenderTest.php
index e660448f42dbb65770e9f59656c59427eda91224..e9eb691b536c6b8d1d7943a60f6b98516e27455b 100644
--- a/core/modules/system/src/Tests/Common/PageRenderTest.php
+++ b/core/modules/system/src/Tests/Common/PageRenderTest.php
@@ -33,24 +33,6 @@ function testHookPageAlter() {
     $this->assertPageRenderHookExceptions('common_test', 'hook_page_attachments_alter');
   }
 
-  /**
-   * Tests hook_page_build() exceptions, a deprecated hook kept around for BC.
-   */
-  function testHookPageBuildExceptions() {
-    // Also enable the system module, because that module invokes the BC hooks.
-    $this->enableModules(['bc_test', 'system']);
-    $this->assertPageRenderHookExceptions('bc_test', 'hook_page_build');
-  }
-
-  /**
-   * Tests hook_page_alter(), a deprecated hook kept around for BC.
-   */
-  function testHookPageAttachmentsAlter() {
-    // Also enable the system module, because that module invokes the BC hooks.
-    $this->enableModules(['bc_test', 'system']);
-    $this->assertPageRenderHookExceptions('bc_test', 'hook_page_alter');
-  }
-
   /**
    * Asserts whether expected exceptions are thrown for invalid hook implementations.
    *
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index ba268445def101856c5e62c0a703864710813dd3..9334a8881e339390807868fe1bea1629fffc9501 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -632,28 +632,6 @@ function system_page_attachments(array &$page) {
       )
     );
   }
-
-  // Invoke hook_page_build() for modules and hook_page_alter() for both modules
-  // and themes, for backwards compatibility.
-  $attachments = [];
-  foreach (\Drupal::moduleHandler()->getImplementations('page_build') as $module) {
-    $function = $module . '_page_build';
-    $function($attachments);
-  }
-  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
-    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_build().');
-  }
-  \Drupal::moduleHandler()->alter('page', $attachments);
-  \Drupal::theme()->alter('page', $attachments);
-  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
-    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_alter().');
-  }
-  if (isset($attachments['#attached'])) {
-    $page['#attached'] = $attachments['#attached'];
-  }
-  if (isset($attachments['#post_render_cache'])) {
-    $page['#post_render_cache'] = $attachments['#post_render_cache'];
-  }
 }
 
 /**
diff --git a/core/modules/system/tests/modules/bc_test/bc_test.info.yml b/core/modules/system/tests/modules/bc_test/bc_test.info.yml
deleted file mode 100644
index 20dbd821dbacc4eca9a58b48042060c20076639d..0000000000000000000000000000000000000000
--- a/core/modules/system/tests/modules/bc_test/bc_test.info.yml
+++ /dev/null
@@ -1,6 +0,0 @@
-name: 'Backwards Compatibility Test'
-type: module
-description: 'Support module for backwards compatibility tests.'
-package: Testing
-version: VERSION
-core: 8.x
diff --git a/core/modules/system/tests/modules/bc_test/bc_test.module b/core/modules/system/tests/modules/bc_test/bc_test.module
deleted file mode 100644
index 537acb83797b3319c32448df0397ed58cd64e8f8..0000000000000000000000000000000000000000
--- a/core/modules/system/tests/modules/bc_test/bc_test.module
+++ /dev/null
@@ -1,44 +0,0 @@
-<?php
-
-/**
- * @file
- * Helper module for backwards compatibility (BC) tests.
- */
-
-/**
- * Implements hook_page_build().
- *
- * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
- */
-function bc_test_page_build(&$page) {
-  $page['#attached']['library'][] = 'core/jquery';
-
-  if (\Drupal::state()->get('bc_test.hook_page_build.descendant_attached', FALSE)) {
-    $page['content']['#attached']['library'][] = 'core/jquery';
-  }
-
-  if (\Drupal::state()->get('bc_test.hook_page_build.render_array', FALSE)) {
-    $page['something'] = [
-      '#markup' => 'test',
-    ];
-  }
-}
-
-/**
- * Implements hook_page_alter().
- *
- * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
- */
-function bc_test_page_alter(&$page) {
-  $page['#attached']['library'][] = 'core/jquery';
-
-  if (\Drupal::state()->get('bc_test.hook_page_alter.descendant_attached', FALSE)) {
-    $page['content']['#attached']['library'][] = 'core/jquery';
-  }
-
-  if (\Drupal::state()->get('bc_test.hook_page_alter.render_array', FALSE)) {
-    $page['something'] = [
-      '#markup' => 'test',
-    ];
-  }
-}
diff --git a/core/modules/system/tests/modules/common_test/common_test.module b/core/modules/system/tests/modules/common_test/common_test.module
index 97ff0bf22b7baf231bf1503bf992723373e5c51f..a1100b43c0eb3cf098a5459735d89265245bcc10 100644
--- a/core/modules/system/tests/modules/common_test/common_test.module
+++ b/core/modules/system/tests/modules/common_test/common_test.module
@@ -260,7 +260,8 @@ function common_test_post_render_cache_placeholder(array $element, array $contex
  * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
  */
 function common_test_page_attachments(array &$page) {
-  $page['#attached']['library'][] = 'core/jquery';
+  $page['#attached']['library'][] = 'core/foo';
+  $page['#attached']['library'][] = 'core/bar';
 
   if (\Drupal::state()->get('common_test.hook_page_attachments.descendant_attached', FALSE)) {
     $page['content']['#attached']['library'][] = 'core/jquery';
@@ -279,7 +280,12 @@ function common_test_page_attachments(array &$page) {
  * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
  */
 function common_test_page_attachments_alter(array &$page) {
-  $page['#attached']['library'][] = 'core/jquery';
+  // Remove a library that was added in common_test_page_attachments(), to test
+  // that this hook can do what it claims to do.
+  if (isset($page['#attached']['library']) && ($index = array_search('core/bar', $page['#attached']['library'])) && $index !== FALSE) {
+    unset($page['#attached']['library'][$index]);
+  }
+  $page['#attached']['library'][] = 'core/baz';
 
   if (\Drupal::state()->get('common_test.hook_page_attachments_alter.descendant_attached', FALSE)) {
     $page['content']['#attached']['library'][] = 'core/jquery';
diff --git a/core/modules/system/theme.api.php b/core/modules/system/theme.api.php
index 1ba2efca421b82fca415f3e4c788a5d5321f4c70..f13210da094031c294d752b19bb30df0283dac97 100644
--- a/core/modules/system/theme.api.php
+++ b/core/modules/system/theme.api.php
@@ -810,60 +810,6 @@ function hook_css_alter(&$css) {
   unset($css[drupal_get_path('module', 'system') . '/defaults.css']);
 }
 
-/**
- * Add attachments (typically assets) to a page before it is rendered.
- *
- * Kept around for backwards compatibility, but now allows only attachments to
- * be added, adding renderable arrays is no longer allowed.
- *
- * @deprecated in Drupal 8.x, will be removed before Drupal 9.0. Successor:
- *   hook_page_attachments(). Is now effectively an alias of that hook.
- *
- * @param $page
- *   The page to which to add attachments.
- *
- * @see hook_page_attachments()
- */
-function hook_page_build(&$page) {
-  $path = drupal_get_path('module', 'foo');
-  // Add JavaScript/CSS assets to all pages.
-  // @see drupal_process_attached()
-  $page['#attached']['js'][$path . '/foo.js'] = array('every_page' => TRUE);
-  $page['#attached']['css'][$path . '/foo.base.css'] = array('every_page' => TRUE);
-  $page['#attached']['css'][$path . '/foo.theme.css'] = array('every_page' => TRUE);
-
-  // Add a special CSS file to a certain page only.
-  if (drupal_is_front_page()) {
-    $page['#attached']['css'][] = $path . '/foo.front.css';
-  }
-}
-
-/**
- * Perform alterations before a page is rendered.
- *
- * Kept around for backwards compatibility, but now allows only attachments to
- * be added, altering the renderable array for the page is no longer allowed.
- *
- * @deprecated in Drupal 8.x, will be removed before Drupal 9.0. Successor:
- *   hook_page_attachments_alter(). Is now effectively an alias of that hook.
- *
- * Use this hook when you want to remove or alter attachments at the page
- * level, or add attachments at the page level that depend on an other module's
- * attachments (this hook runs after hook_page_build().
- *
- * @param $page
- *   An empty renderable array representing the page.
- *
- * @see hook_page_build()
- */
-function hook_page_alter(&$page) {
-  // Conditionally remove an asset.
-  if (in_array('core/jquery', $page['#attached']['library'])) {
-    $index = array_search('core/jquery', $page['#attached']['library']);
-    unset($page['#attached']['library'][$index]);
-  }
-}
-
 /**
  * Add attachments (typically assets) to a page before it is rendered.
  *
diff --git a/core/modules/views/views.module b/core/modules/views/views.module
index f2a0b376844e8ce7a7d1d395f0b1515a7fca4b91..507758c05c41d627fa7bf394ab5839472edb9dca 100644
--- a/core/modules/views/views.module
+++ b/core/modules/views/views.module
@@ -388,7 +388,7 @@ function views_preprocess_html(&$variables) {
  *   The ID of the display within $view whose contextual links will be added.
  *
  * @see \Drupal\views\Plugin\block\block\ViewsBlock::addContextualLinks()
- * @see views_page_alter()
+ * @see views_preprocess_page()
  * @see template_preprocess_views_view()
  */
 function views_add_contextual_links(&$render_element, $location, ViewExecutable $view, $display_id) {