diff -u b/core/modules/media_library/config/install/views.view.media_library.yml b/core/modules/media_library/config/install/views.view.media_library.yml
--- b/core/modules/media_library/config/install/views.view.media_library.yml
+++ b/core/modules/media_library/config/install/views.view.media_library.yml
@@ -8,6 +8,7 @@
       - media_library
   module:
     - media
+    - media_library
     - user
 id: media_library
 label: 'Media library'
@@ -416,6 +417,166 @@
       footer: {  }
       empty: {  }
       relationships: {  }
+      display_extenders: {  }
+      use_ajax: true
+      css_class: media-library-view
+    cache_metadata:
+      max-age: 0
+      contexts:
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'url.query_args:sort_by'
+        - user.permissions
+      tags: {  }
+  page:
+    display_plugin: page
+    id: page
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: admin/content/media
+      menu:
+        type: tab
+        title: Media
+        description: 'Allows users to browse and administer media items'
+        expanded: false
+        parent: system.admin_content
+        weight: 5
+        context: '0'
+        menu_name: admin
+    cache_metadata:
+      max-age: 0
+      contexts:
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'url.query_args:sort_by'
+        - user.permissions
+      tags: {  }
+  widget:
+    display_plugin: page
+    id: widget
+    display_title: Widget
+    position: 2
+    display_options:
+      display_extenders: {  }
+      path: admin/content/media-widget
+      fields:
+        rendered_entity:
+          id: rendered_entity
+          table: media
+          field: rendered_entity
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: media-library-item__content
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          view_mode: media_library
+          entity_type: media
+          plugin_id: rendered_entity
+        media_library_select_form:
+          id: media_library_select_form
+          table: media
+          field: media_library_select_form
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: click-to-select-checkbox
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          entity_type: media
+          plugin_id: media_library_select_form
+      defaults:
+        fields: false
+      display_description: ''
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'url.query_args:sort_by'
+        - user.permissions
+      tags: {  }
       arguments:
         bundle:
           id: bundle
@@ -464,35 +624,0 @@
-    cache_metadata:
-      max-age: 0
-      contexts:
-        - 'languages:language_interface'
-        - url
-        - url.query_args
-        - 'url.query_args:sort_by'
-        - user.permissions
-      tags: {  }
-  page:
-    display_plugin: page
-    id: page
-    display_title: Page
-    position: 1
-    display_options:
-      display_extenders: {  }
-      path: admin/content/media
-      menu:
-        type: tab
-        title: Media
-        description: 'Allows users to browse and administer media items'
-        expanded: false
-        parent: system.admin_content
-        weight: 5
-        context: '0'
-        menu_name: admin
-    cache_metadata:
-      max-age: 0
-      contexts:
-        - 'languages:language_interface'
-        - url
-        - url.query_args
-        - 'url.query_args:sort_by'
-        - user.permissions
-      tags: {  }
diff -u b/core/modules/media_library/css/media_library.css b/core/modules/media_library/css/media_library.css
--- b/core/modules/media_library/css/media_library.css
+++ b/core/modules/media_library/css/media_library.css
@@ -2,7 +2,8 @@
 * @file media_library.view.css
 */
 
-.media-library-view .view-content form {
+.media-library-view .view-content form,
+.media-library-selection {
   display: flex;
   flex-wrap: wrap;
   align-content: space-between;
@@ -137,0 +139,50 @@
+
+.media-library-selection {
+  margin-bottom: 1.5rem;
+}
+
+.media-library-selection .media-library-item__preview {
+  cursor: move;
+}
+
+.media-library-selection .media-library-item::after {
+  display: none;
+}
+
+.media-library-item .media-library-item-remove {
+  position: absolute;
+  z-index: 1;
+  top: 0;
+  right: 0;
+  width: 24px;
+  height: 24px;
+  margin: 5px;
+  padding: 0;
+  background: url('../../../misc/icons/787878/ex.svg') #ffffff center no-repeat;
+  background-size: 16px 16px;
+  border: 2px solid #ccc;
+  border-radius: 20px;
+  color: transparent;
+  text-shadow: none;
+  transition: .2s border-color;
+}
+
+.media-library-item .media-library-item-remove:hover,
+.media-library-item .media-library-item-remove:focus,
+.media-library-item .media-library-item-remove.button:disabled {
+  border-color: #40b6ff;
+  background: url('../../../misc/icons/787878/ex.svg') #ffffff center no-repeat;
+  background-size: 16px 16px;
+  color: transparent;
+  text-shadow: none;
+}
+
+.media-library-toggle-weight {
+  position: absolute;
+  right: 5px;
+  top: 5px;
+}
+
+.media-library-item .form-item {
+  margin: .75em;
+}
diff -u b/core/modules/media_library/media_library.libraries.yml b/core/modules/media_library/media_library.libraries.yml
--- b/core/modules/media_library/media_library.libraries.yml
+++ b/core/modules/media_library/media_library.libraries.yml
@@ -23,0 +24,10 @@
+
+widget:
+  version: VERSION
+  js:
+    js/media_library.widget.js: {}
+  dependencies:
+    - core/drupal
+    - core/jquery
+    - core/jquery.ui.sortable
+    - media_library/view
diff -u b/core/modules/media_library/media_library.module b/core/modules/media_library/media_library.module
--- b/core/modules/media_library/media_library.module
+++ b/core/modules/media_library/media_library.module
@@ -41,6 +41,11 @@
 function media_library_views_post_render(ViewExecutable $view, &$output, CachePluginBase $cache) {
   if ($view->id() === 'media_library') {
     $output['#attached']['library'][] = 'media_library/view';
+    // Ensure that the widget ID passed to the modal persists across rebuilds.
+    $request = \Drupal::request();
+    if ($request->query->has('media_library_widget_id')) {
+      $output['#attached']['drupalSettings']['views']['ajax_path'] .= '?media_library_widget_id=' . $request->query->get('media_library_widget_id');
+    }
   }
 }
 
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/js/media_library.widget.es6.js
@@ -0,0 +1,62 @@
+/**
+ * @file media_library.widget.js
+ */
+
+(function ($, Drupal) {
+
+  "use strict";
+
+  /**
+   * Provides custom JS behaviors related to the media library field widget.
+   */
+  Drupal.behaviors.MediaLibraryWidget = {
+    attach: function (context) {
+      // Allow media items to be re-sorted with drag+drop in the widget.
+      $('.media-library-selection', context).once('media-library-sortable').sortable({
+        tolerance: 'pointer',
+        helper: 'clone',
+        handle: '.media-library-item__preview',
+        stop: function(event, ui) {
+          // Update all the hidden "weight" fields.
+          $(event.target).children().each(function (index) {
+            $(this).find('.media-library-item-weight').val(index);
+          });
+        }
+      });
+      // Allow item order to be set without drag+drop for accessibility.
+      $('.media-library-toggle-weight', context).once('media-library-toggle')
+        .attr('title', Drupal.t('Re-order media by numerical weight instead of dragging.'))
+        .on('click', function (e) {
+          e.preventDefault();
+          $('.media-library-item-weight').parent().toggle();
+        })
+        .text(Drupal.t('Toggle media item weights'));
+      $('.media-library-item-weight', context).once('media-library-toggle').parent().hide();
+      // Warn users when clicking outgoing links from the library or widget.
+      $('.media-library-item a[href]', context).once('media-library-warn-link')
+        .on('click', function (e) {
+          const message = Drupal.t('Unsaved changes to the form will be lost. Are you sure you want to leave?');
+          const confirmation = window.confirm(message);
+          if (!confirmation) {
+            e.preventDefault();
+          }
+        });
+    }
+  };
+
+  /**
+   * Ajax command to add items to the media widget.
+   *
+   * @param {Drupal.Ajax} ajax
+   *   {@link Drupal.Ajax} object created by {@link Drupal.ajax}.
+   * @param {object} response
+   *   JSON response from the Ajax request.
+   * @param {number} [status]
+   *   XMLHttpRequest status.
+   */
+  Drupal.AjaxCommands.prototype.addMediaToWidget = function (ajax, response, status) {
+    $(`[data-media-library-widget-value="${response.identifier}"]`).val(response.mids.join(','));
+    $(`[data-media-library-widget-update="${response.identifier}"]`).trigger('mousedown');
+  };
+
+})(jQuery, Drupal);
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/js/media_library.widget.js
@@ -0,0 +1,45 @@
+/**
+* DO NOT EDIT THIS FILE.
+* See the following change record for more information,
+* https://www.drupal.org/node/2815083
+* @preserve
+**/
+
+(function ($, Drupal) {
+
+  "use strict";
+
+  Drupal.behaviors.MediaLibraryWidget = {
+    attach: function attach(context) {
+      $('.media-library-selection', context).once('media-library-sortable').sortable({
+        tolerance: 'pointer',
+        helper: 'clone',
+        handle: '.media-library-item__preview',
+        stop: function stop(event, ui) {
+          $(event.target).children().each(function (index) {
+            $(this).find('.media-library-item-weight').val(index);
+          });
+        }
+      });
+
+      $('.media-library-toggle-weight', context).once('media-library-toggle').attr('title', Drupal.t('Re-order media by numerical weight instead of dragging.')).on('click', function (e) {
+        e.preventDefault();
+        $('.media-library-item-weight').parent().toggle();
+      }).text(Drupal.t('Toggle media item weights'));
+      $('.media-library-item-weight', context).once('media-library-toggle').parent().hide();
+
+      $('.media-library-item a[href]', context).once('media-library-warn-link').on('click', function (e) {
+        var message = Drupal.t('Unsaved changes to the form will be lost. Are you sure you want to leave?');
+        var confirmation = window.confirm(message);
+        if (!confirmation) {
+          e.preventDefault();
+        }
+      });
+    }
+  };
+
+  Drupal.AjaxCommands.prototype.addMediaToWidget = function (ajax, response, status) {
+    $('[data-media-library-widget-value="' + response.identifier + '"]').val(response.mids.join(','));
+    $('[data-media-library-widget-update="' + response.identifier + '"]').trigger('mousedown');
+  };
+})(jQuery, Drupal);
\ No newline at end of file
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/media_library.views.inc
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ * Contains views integration for the media_library module.
+ */
+
+/**
+ * Implements hook_views_data().
+ */
+function media_library_views_data() {
+  $data = [];
+  $data['media']['media_library_select_form'] = [
+    'title' => t('Select media'),
+    'help' => t('Provides a field for selecting media entities in our media library view'),
+    'real field' => 'mid',
+    'field' => [
+      'id' => 'media_library_select_form',
+    ],
+  ];
+  return $data;
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/src/Ajax/AddMediaToWidget.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Drupal\media_library\Ajax;
+
+use Drupal\Core\Ajax\CommandInterface;
+
+/**
+ * Ajax command to add Media items to a field widget.
+ *
+ * This widget enables communication between Media forms, usually between a
+ * form that creates or selects media, and a field widget.
+ *
+ * The identifier property is used to select two elements on the field widget:
+ *   - [data-media-library-widget-value="<identifier>"]
+ *       An input element that will store new MIDs.
+ *   - [data-media-library-widget-update="<identifier>"]
+ *       An AJAX button that will be clicked to inform the widget of an update.
+ *
+ * @ingroup ajax
+ */
+class AddMediaToWidget implements CommandInterface {
+
+  /**
+   * Media IDs to pass to a field widget.
+   *
+   * @var array
+   */
+  protected $mids;
+
+  /**
+   * An identifier for the field widget.
+   *
+   * @var string
+   */
+  protected $identifier;
+
+  /**
+   * AddMediaToWidget constructor.
+   *
+   * @param array $mids
+   *   Media IDs to pass to a field widget.
+   * @param string $identifier
+   *   An identifier for the field widget.
+   */
+  public function __construct(array $mids, $identifier) {
+    $this->mids = $mids;
+    $this->identifier = $identifier;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render() {
+    return [
+      'command' => 'addMediaToWidget',
+      'mids' => $this->mids,
+      'identifier' => $this->identifier,
+    ];
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php
@@ -0,0 +1,443 @@
+<?php
+
+namespace Drupal\media_library\Plugin\Field\FieldWidget;
+
+use Drupal\Component\Utility\NestedArray;
+use Drupal\Component\Utility\SortArray;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Field\WidgetBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Url;
+use Drupal\media\Entity\Media;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Validator\ConstraintViolationInterface;
+
+/**
+ * Plugin implementation of the 'media_library_widget' widget.
+ *
+ * @FieldWidget(
+ *   id = "media_library_widget",
+ *   label = @Translation("Media library"),
+ *   description = @Translation("Allows you to re-use Media Entities."),
+ *   field_types = {
+ *     "entity_reference"
+ *   },
+ *   multiple_values = TRUE
+ * )
+ */
+class MediaLibraryWidget extends WidgetBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * Entity type manager service.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Constructs a MediaLibraryWidget widget.
+   *
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
+   *   The definition of the field to which the widget is associated.
+   * @param array $settings
+   *   The widget settings.
+   * @param array $third_party_settings
+   *   Any third party settings.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   Entity type manager service.
+   */
+  public function __construct($plugin_id, $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, array $third_party_settings, EntityTypeManagerInterface $entity_type_manager) {
+    parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $third_party_settings);
+    $this->entityTypeManager = $entity_type_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $plugin_id,
+      $plugin_definition,
+      $configuration['field_definition'],
+      $configuration['settings'],
+      $configuration['third_party_settings'],
+      $container->get('entity_type.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function isApplicable(FieldDefinitionInterface $field_definition) {
+    return $field_definition->getSetting('target_type') === 'media';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(FieldItemListInterface $items, array &$form, FormStateInterface $form_state, $get_delta = NULL) {
+    $field_name = $this->fieldDefinition->getName();
+    $parents = $form['#parents'];
+
+    // Load the items for form rebuilds from the field state.
+    $field_state = static::getWidgetState($parents, $field_name, $form_state);
+    if ($field_state && isset($field_state['items'])) {
+      usort($field_state['items'], [SortArray::class, 'sortByWeightElement']);
+      $items->setValue($field_state['items']);
+    }
+
+    $build = parent::form($items, $form, $form_state, $get_delta);
+
+    return $build;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+    /** @var \Drupal\Core\Field\EntityReferenceFieldItemListInterface $items */
+    $referenced_entities = $items->referencedEntities();
+    $view_builder = $this->entityTypeManager->getViewBuilder($this->getFieldSetting('target_type'));
+    $field_name = $this->fieldDefinition->getName();
+    $parents = $form['#parents'];
+    $id_suffix = '-' . implode('-', $parents);
+    $wrapper_id = $field_name . '-media-library-wrapper' . $id_suffix;
+
+    $settings = $this->getFieldSetting('handler_settings');
+    $element += [
+      '#type' => 'fieldset',
+      '#cardinality' => $this->fieldDefinition->getFieldStorageDefinition()->getCardinality(),
+      '#target_bundles' => isset($settings['target_bundles']) ? $settings['target_bundles'] : FALSE,
+      'selection' => [
+        '#type' => 'container',
+        '#attributes' => [
+          'class' => 'media-library-selection',
+        ],
+      ],
+      '#attributes' => [
+        'id' => $wrapper_id,
+        'class' => ['media-library-wrapper'],
+      ],
+      '#attached' => [
+        'library' => ['media_library/widget'],
+      ],
+    ];
+
+    if (empty($referenced_entities)) {
+      $element['empty_selection'] = [
+        '#markup' => $this->t('<p>No media selected.</p>'),
+      ];
+    }
+    else {
+      $element['weight_toggle'] = [
+        '#type' => 'html_tag',
+        '#tag' => 'button',
+        '#value' => $this->t('Toggle media item weights'),
+        '#attributes' => [
+          'class' => ['link', 'media-library-toggle-weight'],
+        ],
+      ];
+
+      foreach ($referenced_entities as $delta => $media_item) {
+        $element['selection'][$delta] = [
+          '#type' => 'container',
+          '#attributes' => [
+            'class' => ['media-library-item', 'media-library-item-in-widget'],
+          ],
+          'preview' => [
+            '#type' => 'container',
+            'view' => $view_builder->view($media_item, 'media_library'),
+            'remove_button' => [
+              '#type' => 'submit',
+              '#media_library_remove_delta' => $delta,
+              '#name' => $field_name . '-' . $delta . '-media-library-remove-button' . $id_suffix,
+              '#value' => $this->t('Remove'),
+              '#attributes' => [
+                'class' => ['media-library-item-remove'],
+              ],
+              '#ajax' => [
+                'callback' => [static::class, 'updateWidget'],
+                'wrapper' => $wrapper_id,
+              ],
+              '#submit' => [[static::class, 'removeItem']],
+              '#limit_validation_errors' => [array_merge($form['#parents'], [$field_name])],
+            ],
+          ],
+          'target_id' => [
+            '#type' => 'hidden',
+            '#value' => $media_item->id(),
+          ],
+          // This hidden value can be toggled visible for accessibility.
+          'weight' => [
+            '#type' => 'textfield',
+            '#title' => $this->t('Weight'),
+            '#default_value' => $delta,
+            '#attributes' => [
+              'class' => ['media-library-item-weight'],
+            ],
+          ],
+        ];
+      }
+    }
+
+    // @todo Contextual filters only work the first time the modal is loaded.
+    // Investigate and file an issue for Views if possible.
+    $element['media_library_open_container'] = [
+      '#type' => 'container',
+      'media_library_open_button' => [
+        '#type' => 'link',
+        '#title' => $this->t('Add Media'),
+        '#name' => $field_name . '-media-library-open-button' . $id_suffix,
+        // @todo Make the View configurable.
+        '#url' => Url::fromRoute('view.media_library.widget', [], [
+          'query' => ['media_library_widget_id' => $field_name . $id_suffix],
+        ]),
+        '#attributes' => [
+          'class' => ['button', 'use-ajax', 'media-library-open-button'],
+          'data-dialog-type' => 'modal',
+          'data-dialog-options' => json_encode([
+            'dialogClass' => 'media-library-widget-modal',
+            'height' => '75%',
+            'width' => '75%',
+            'title' => $this->t('Media library'),
+          ]),
+        ],
+        '#limit_validation_errors' => [array_merge($parents, [$field_name])],
+      ],
+    ];
+
+    // Add a hidden textfield to the form, which is filled by returning the
+    // \Drupal\media_library\Ajax\AddMediaToWidget command.
+    $element['media_library_selection'] = [
+      '#type' => 'textfield',
+      '#attributes' => [
+        'data-media-library-widget-value' => $field_name . $id_suffix,
+        'class' => ['visually-hidden'],
+      ],
+    ];
+
+    // This hidden button can be pressed to update the widget based on newly
+    // selected items.
+    $element['media_library_update_widget'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Update widget'),
+      '#name' => $field_name . '-media-library-update' . $id_suffix,
+      '#ajax' => [
+        'callback' => [static::class, 'updateWidget'],
+        'wrapper' => $wrapper_id,
+      ],
+      '#attributes' => [
+        'data-media-library-widget-update' => $field_name . $id_suffix,
+        'class' => ['visually-hidden', 'media-library-update'],
+      ],
+      '#validate' => [[static::class, 'validateItems']],
+      '#submit' => [[static::class, 'updateItems']],
+      '#limit_validation_errors' => [array_merge($parents, [$field_name])],
+    ];
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function errorElement(array $element, ConstraintViolationInterface $error, array $form, FormStateInterface $form_state) {
+    return isset($element['target_id']) ? $element['target_id'] : FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function massageFormValues(array $values, array $form, FormStateInterface $form_state) {
+    if (isset($values['selection'])) {
+      usort($values['selection'], [SortArray::class, 'sortByWeightElement']);
+      return $values['selection'];
+    }
+    else {
+      return [];
+    }
+  }
+
+  /**
+   * AJAX callback to update the widget when the selection changes.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   *
+   * @return array
+   *   An array representing the updated widget.
+   */
+  public static function updateWidget(array $form, FormStateInterface $form_state) {
+    $triggering_element = $form_state->getTriggeringElement();
+    $length = isset($triggering_element['#media_library_remove_delta']) ? -4 : -1;
+    $parents = $triggering_element['#array_parents'];
+    $parents = array_slice($parents, 0, $length);
+    $element = NestedArray::getValue($form, $parents);
+    // Always clear the textfield selection to prevent duplicate additions.
+    $element['media_library_selection']['#value'] = '';
+    return $element;
+  }
+
+  /**
+   * Submit callback for remove buttons.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   */
+  public static function removeItem(array $form, FormStateInterface $form_state) {
+    $triggering_element = $form_state->getTriggeringElement();
+
+    $parents = array_slice($triggering_element['#array_parents'], 0, -4);
+    $element = NestedArray::getValue($form, $parents);
+    $delta = $triggering_element['#media_library_remove_delta'];
+
+    // Find and remove correct entity.
+    $path = $element['#parents'];
+    $values = NestedArray::getValue($form_state->getValues(), $path);
+    $field_state = static::getFieldState($element, $form_state);
+    if (isset($values['selection'])) {
+      if (isset($values['selection'][$delta])) {
+        array_splice($values['selection'], $delta, 1);
+        $field_state['items'] = $values['selection'];
+        $field_state['items_count'] = count($field_state['items']);
+      }
+    }
+    static::setFieldState($element, $form_state, $field_state);
+
+    $form_state->setRebuild();
+  }
+
+  /**
+   * Validates that newly selected items can be added to the widget.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   */
+  public static function validateItems(array $form, FormStateInterface $form_state) {
+    $button = $form_state->getTriggeringElement();
+    $element = NestedArray::getValue($form, array_slice($button['#array_parents'], 0, -1));
+
+    $field_state = self::getFieldState($element, $form_state);
+    $media = self::getNewMediaItems($element, $form_state);
+    if (!empty($media)) {
+      $cardinality_unlimited = ($element['#cardinality'] === FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+      $selection = $field_state['items_count'] + count($media);
+      if (!$cardinality_unlimited && ($selection > $element['#cardinality'])) {
+        $form_state->setError($element, t('More items have been selected than this field allows (max @count).', [
+          '@count' => $element['#cardinality'],
+        ]));
+      }
+      foreach ($media as $media_item) {
+        if ($element['#target_bundles'] && !in_array($media_item->bundle(), $element['#target_bundles'], TRUE)) {
+          $form_state->setError($element, t('The media item "@label" is not of an accepted type.', [
+            '@label' => $media_item->label(),
+          ]));
+        }
+      }
+    }
+  }
+
+  /**
+   * Updates the field state based on the form state and sets the form rebuild.
+   *
+   * @param array $form
+   *   The form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   */
+  public static function updateItems(array $form, FormStateInterface $form_state) {
+    $button = $form_state->getTriggeringElement();
+    $element = NestedArray::getValue($form, array_slice($button['#array_parents'], 0, -1));
+
+    $field_state = self::getFieldState($element, $form_state);
+
+    $media = self::getNewMediaItems($element, $form_state);
+    $field_state['items'] = isset($field_state['items']) ? $field_state['items'] : [];
+    $weight = count($field_state['items']);
+    foreach ($media as $media_item) {
+      if ($media && $media_item->access('view')) {
+        $field_state['items'][] = [
+          'target_id' => $media_item->id(),
+          'weight' => $weight++,
+        ];
+      }
+    }
+
+    $field_state['items_count'] = count($field_state['items']);
+    static::setFieldState($element, $form_state, $field_state);
+
+    $form_state->setRebuild();
+  }
+
+  /**
+   * Gets newly selected media items.
+   *
+   * @param array $element
+   *   The wrapping element for this widget.
+   * @param FormStateInterface $form_state
+   *   The current state of the form.
+   * @return array|\Drupal\media\MediaInterface[]
+   *   An array of selected media items.
+   */
+  public static function getNewMediaItems(array $element, FormStateInterface $form_state) {
+    // Get the new media ids passed to our hidden button.
+    $values = $form_state->getValues();
+    $path = $element['#parents'];
+    $value = NestedArray::getValue($values, $path);
+
+    $media = [];
+    if (!empty($value['media_library_selection'])) {
+      $ids = explode(',', $value['media_library_selection']);
+      /** @var \Drupal\media\MediaInterface[] $media */
+      $media = Media::loadMultiple($ids);
+    }
+    return $media;
+  }
+
+  /**
+   * Gets the field state for the widget.
+   *
+   * @param array $element
+   *   The wrapping element for this widget.
+   * @param FormStateInterface $form_state
+   *   The current state of the form.
+   * @return array|mixed
+   *   The field state.
+   */
+  public static function getFieldState(array $element, FormStateInterface $form_state) {
+    $field_name = $element['#field_name'];
+    $parents = $element['#field_parents'];
+    return static::getWidgetState($parents, $field_name, $form_state);
+  }
+
+  /**
+   * Sets the field state for the widget.
+   *
+   * @param array $element
+   *   The wrapping element for this widget.
+   * @param FormStateInterface $form_state
+   *   The current state of the form.
+   * @param array $field_state
+   *   The field state to set.
+   */
+  public static function setFieldState(array $element, FormStateInterface $form_state, array $field_state) {
+    $field_name = $element['#field_name'];
+    $parents = $element['#field_parents'];
+    static::setWidgetState($parents, $field_name, $form_state, $field_state);
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php
@@ -0,0 +1,129 @@
+<?php
+
+namespace Drupal\media_library\Plugin\views\field;
+
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\CloseDialogCommand;
+use Drupal\Core\Form\FormBuilderInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+use Drupal\media_library\Ajax\AddMediaToWidget;
+use Drupal\views\Plugin\views\field\FieldPluginBase;
+use Drupal\views\Render\ViewsRenderPipelineMarkup;
+use Drupal\views\ResultRow;
+
+/**
+ * Defines a field that outputs a checkbox and form for selecting media.
+ *
+ * @ViewsField("media_library_select_form")
+ */
+class MediaLibrarySelectForm extends FieldPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getValue(ResultRow $row, $field = NULL) {
+    return '<!--form-item-' . $this->options['id'] . '--' . $row->index . '-->';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render(ResultRow $values) {
+    return ViewsRenderPipelineMarkup::create($this->getValue($values));
+  }
+
+  /**
+   * Form constructor for the media library select form.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function viewsForm(array &$form, FormStateInterface $form_state) {
+    // Only add the bulk form options and buttons if there are results.
+    if (!empty($this->view->result)) {
+      // Render checkboxes for all rows.
+      $form[$this->options['id']]['#tree'] = TRUE;
+      foreach ($this->view->result as $row_index => $row) {
+        $entity = $this->getEntity($row);
+        $form[$this->options['id']][$row_index] = [
+          '#type' => 'checkbox',
+          '#title' => $this->t('Select this item'),
+          '#title_display' => 'invisible',
+          '#return_value' => $entity->getEntityTypeId() . ':' . $entity->id(),
+        ];
+      }
+
+      // @todo Remove in https://www.drupal.org/project/drupal/issues/2504115
+      $url = parse_url($form['#action'], PHP_URL_PATH);
+
+      $form['actions']['submit']['#ajax'] = [
+        'url' => Url::fromUserInput($url),
+        'options' => [
+          'query' => \Drupal::request()->query->all() + [
+            FormBuilderInterface::AJAX_FORM_REQUEST => TRUE,
+          ],
+        ],
+        'callback' => [static::class, 'updateWidget'],
+      ];
+
+      $form['actions']['submit']['#value'] = $this->t('Select media');
+      $form['actions']['submit']['#field_id'] = $this->options['id'];
+    }
+  }
+
+  /**
+   * Submit handler for the media library select form.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse
+   *   A command to send the selection to the current field widget.
+   *
+   */
+  public static function updateWidget(array &$form, FormStateInterface $form_state) {
+    $response = new AjaxResponse();
+    $widget_id = \Drupal::request()->query->get('media_library_widget_id');
+    if ($widget_id && is_string($widget_id)) {
+      $field_id = $form_state->getTriggeringElement()['#field_id'];
+      $selected = array_values(array_filter($form_state->getValue($field_id, [])));
+      $mids = str_replace('media:', '', $selected);
+      $response->addCommand(new AddMediaToWidget($mids, $widget_id));
+      $response->addCommand(new CloseDialogCommand());
+    }
+    return $response;
+  }
+
+  /**
+   * Returns the message to be displayed when there are no selected items.
+   *
+   * @return string
+   *   Message displayed when no items are selected.
+   */
+  protected function emptySelectedMessage() {
+    return $this->t('No items selected.');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewsFormValidate(array &$form, FormStateInterface $form_state) {
+    $selected = array_filter($form_state->getValue($this->options['id']));
+    if (empty($selected)) {
+      $form_state->setErrorByName('', $this->emptySelectedMessage());
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function clickSortable() {
+    return FALSE;
+  }
+
+}