diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index d755c6f7e6..bbeceae211 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -331,6 +331,27 @@ public function isDefaultRevision($new_value = NULL) {
     return $this->isNew() || $return;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function wasDefaultRevision() {
+    /** @var \Drupal\Core\Entity\ContentEntityTypeInterface $entity_type */
+    $entity_type = $this->getEntityType();
+    if (!$entity_type->isRevisionable()) {
+      return TRUE;
+    }
+
+    $revision_default_key = $entity_type->getRevisionMetadataKey('revision_default');
+    $value = $this->isNew() || $this->get($revision_default_key)->value;
+
+    if (isset($value)) {
+      return (bool) $value;
+    }
+    else {
+      throw new \LogicException("Missing data for the '$revision_default_key' field on the entity {$this->getEntityTypeId()}:{$this->id()}.");
+    }
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
index 7f36c11a67..cef3742ac1 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
@@ -375,6 +375,13 @@ protected function doSave($id, EntityInterface $entity) {
     }
 
     $this->populateAffectedRevisionTranslations($entity);
+
+    // Populate the "revision_default" flag.
+    if ($this->entityType->isRevisionable()) {
+      $revision_default_key = $this->entityType->getRevisionMetadataKey('revision_default');
+      $entity->set($revision_default_key, $entity->isDefaultRevision());
+    }
+
     $this->doSaveFieldItems($entity);
 
     return $return;
diff --git a/core/lib/Drupal/Core/Entity/ContentEntityType.php b/core/lib/Drupal/Core/Entity/ContentEntityType.php
index 0e26c3bb51..5be34c9ba5 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityType.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityType.php
@@ -19,10 +19,15 @@ class ContentEntityType extends EntityType implements ContentEntityTypeInterface
    */
   public function __construct($definition) {
     parent::__construct($definition);
+
     $this->handlers += [
       'storage' => 'Drupal\Core\Entity\Sql\SqlContentEntityStorage',
       'view_builder' => 'Drupal\Core\Entity\EntityViewBuilder',
     ];
+
+    $this->revision_metadata_keys += [
+      'revision_default' => 'revision_default',
+    ];
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/EntityFieldManager.php b/core/lib/Drupal/Core/Entity/EntityFieldManager.php
index 63c35e9743..0c699b0332 100644
--- a/core/lib/Drupal/Core/Entity/EntityFieldManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityFieldManager.php
@@ -190,8 +190,10 @@ public function getBaseFieldDefinitions($entity_type_id) {
    *   flagged as translatable.
    */
   protected function buildBaseFieldDefinitions($entity_type_id) {
+    /** @var \Drupal\Core\Entity\ContentEntityTypeInterface $entity_type */
     $entity_type = $this->entityTypeManager->getDefinition($entity_type_id);
     $class = $entity_type->getClass();
+    /** @var string[] $keys */
     $keys = array_filter($entity_type->getKeys());
 
     // Fail with an exception for non-fieldable entity types.
@@ -221,6 +223,17 @@ protected function buildBaseFieldDefinitions($entity_type_id) {
     }
 
     // Make sure that revisionable entity types are correctly defined.
+    if ($entity_type->isRevisionable()) {
+      $field_name = $entity_type->getRevisionMetadataKey('revision_default');
+      $base_field_definitions[$field_name] = BaseFieldDefinition::create('boolean')
+        ->setLabel($this->t('Default revision'))
+        ->setDescription($this->t('A flag indicating whether this was a default revision when it was saved.'))
+        ->setTranslatable(FALSE)
+        ->setRevisionable(TRUE);
+    }
+
+    // Make sure that revisionable and translatable entity types are correctly
+    // defined.
     if ($entity_type->isRevisionable() && $entity_type->isTranslatable()) {
       // The 'revision_translation_affected' field should always be defined.
       // This field has been added unconditionally in Drupal 8.4.0 and it is
diff --git a/core/lib/Drupal/Core/Entity/RevisionableInterface.php b/core/lib/Drupal/Core/Entity/RevisionableInterface.php
index e25bc25443..5987580319 100644
--- a/core/lib/Drupal/Core/Entity/RevisionableInterface.php
+++ b/core/lib/Drupal/Core/Entity/RevisionableInterface.php
@@ -51,6 +51,17 @@ public function getRevisionId();
    */
   public function isDefaultRevision($new_value = NULL);
 
+  /**
+   * Checks whether the entity object was a default revision when it was saved.
+   *
+   * @return bool
+   *   TRUE if the entity object was a revision, FALSE otherwise.
+   *
+   * @throws \LogicException
+   *   If the default revision data is missing.
+   */
+  public function wasDefaultRevision();
+
   /**
    * Checks if this entity is the latest revision.
    *
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
index 60712eeb21..db46d05999 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
@@ -245,6 +245,7 @@ protected function copyData(array &$sandbox) {
     $original_base_table = $original_entity_type->getBaseTable();
 
     $revision_id_key = $temporary_entity_type->getKey('revision');
+    $revision_default_key = $temporary_entity_type->getRevisionMetadataKey('revision_default');
     $revision_translation_affected_key = $temporary_entity_type->getKey('revision_translation_affected');
 
     // If 'progress' is not set, then this will be the first run of the batch.
@@ -288,6 +289,10 @@ protected function copyData(array &$sandbox) {
         // Set the revision ID to be same as the entity ID.
         $entity->set($revision_id_key, $entity_id);
 
+        // We had no revisions so far, so the existing data belongs to the
+        // default revision now.
+        $entity->set($revision_default_key, TRUE);
+
         // Set the 'revision_translation_affected' flag to TRUE to match the
         // previous API return value: if the field was not defined the value
         // returned was always TRUE.
@@ -380,6 +385,22 @@ protected function updateFieldStorageDefinitionsToRevisionable(ContentEntityType
     }
     $updated_storage_definitions[$entity_type->getKey('revision')] = $revision_field;
 
+    // Add the default revision flag field.
+    $field_name = $entity_type->getRevisionMetadataKey('revision_default');
+    $storage_definition = BaseFieldDefinition::create('boolean')
+      ->setName($field_name)
+      ->setTargetEntityTypeId($entity_type->id())
+      ->setTargetBundle(NULL)
+      ->setLabel(t('Default revision'))
+      ->setDescription(t('A flag indicating whether this was a default revision when it was saved.'))
+      ->setTranslatable(FALSE)
+      ->setRevisionable(TRUE);
+
+    if ($update_cached_definitions) {
+      $this->entityDefinitionUpdateManager->installFieldStorageDefinition($field_name, $entity_type->id(), $entity_type->getProvider(), $storage_definition);
+    }
+    $updated_storage_definitions[$field_name] = $storage_definition;
+
     // Add the 'revision_translation_affected' field if needed.
     if ($entity_type->isTranslatable()) {
       $revision_translation_affected_field = BaseFieldDefinition::create('boolean')
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/BlockContent/BlockContentResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/BlockContent/BlockContentResourceTestBase.php
index 5766817940..f5b3fdcc15 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/BlockContent/BlockContentResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/BlockContent/BlockContentResourceTestBase.php
@@ -122,6 +122,11 @@ protected function getExpectedNormalizedEntity() {
           'value' => TRUE,
         ],
       ],
+      'revision_default' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
       'default_langcode' => [
         [
           'value' => TRUE,
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
index 1875d004a4..430b731be7 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
@@ -212,6 +212,11 @@ protected function getExpectedNormalizedEntity() {
           'value' => TRUE,
         ],
       ],
+      'revision_default' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
     ];
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
index bf0ba7a591..fc827ace16 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
@@ -152,6 +152,11 @@ protected function getExpectedNormalizedEntity() {
           'value' => TRUE,
         ],
       ],
+      'revision_default' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
       'default_langcode' => [
         [
           'value' => TRUE,
diff --git a/core/modules/serialization/tests/src/Kernel/EntitySerializationTest.php b/core/modules/serialization/tests/src/Kernel/EntitySerializationTest.php
index 5df9d75db0..8e9204e022 100644
--- a/core/modules/serialization/tests/src/Kernel/EntitySerializationTest.php
+++ b/core/modules/serialization/tests/src/Kernel/EntitySerializationTest.php
@@ -150,6 +150,9 @@ public function testNormalize() {
       'default_langcode' => [
         ['value' => TRUE],
       ],
+      'revision_default' => [
+        ['value' => TRUE],
+      ],
       'revision_translation_affected' => [
         ['value' => TRUE],
       ],
@@ -225,6 +228,7 @@ public function testSerialize() {
       'user_id' => '<user_id><target_id>' . $this->user->id() . '</target_id><target_type>' . $this->user->getEntityTypeId() . '</target_type><target_uuid>' . $this->user->uuid() . '</target_uuid><url>' . $this->user->url() . '</url></user_id>',
       'revision_id' => '<revision_id><value>' . $this->entity->getRevisionId() . '</value></revision_id>',
       'default_langcode' => '<default_langcode><value>1</value></default_langcode>',
+      'revision_default' => '<revision_default><value>1</value></revision_default>',
       'revision_translation_affected' => '<revision_translation_affected><value>1</value></revision_translation_affected>',
       'non_rev_field' => '<non_rev_field/>',
       'field_test_text' => '<field_test_text><value>' . $this->values['field_test_text']['value'] . '</value><format>' . $this->values['field_test_text']['format'] . '</format><processed><![CDATA[<p>' . $this->values['field_test_text']['value'] . '</p>]]></processed></field_test_text>',
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index ef6f124f51..3f59d9e8c1 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2056,3 +2056,47 @@ function system_update_8403() {
     }
   }
 }
+
+/**
+ * Add the 'revision_default' field to all relevant entity types.
+ */
+function system_update_8501() {
+  $definition_update_manager = \Drupal::entityDefinitionUpdateManager();
+
+  // Clear the cached entity type definitions so we get the new
+  // 'revision_default' entity key.
+  \Drupal::entityTypeManager()->clearCachedDefinitions();
+
+  // Get a list of revisionable entity types.
+  /** @var \Drupal\Core\Entity\ContentEntityTypeInterface[] $definitions */
+  $definitions = array_filter(\Drupal::entityTypeManager()->getDefinitions(), function (EntityTypeInterface $entity_type) use ($definition_update_manager) {
+    if ($entity_type = $definition_update_manager->getEntityType($entity_type->id())) {
+      return $entity_type->isRevisionable();
+    }
+    return FALSE;
+  });
+
+  // Install the 'revision_default' field.
+  foreach ($definitions as $entity_type_id => $entity_type) {
+    $field_name = $entity_type->getRevisionMetadataKey('revision_default');
+    // Install the 'revision_translation_affected' field if needed.
+    if (!$definition_update_manager->getFieldStorageDefinition($field_name, $entity_type_id)) {
+      // Make sure the new "revision_default" entity key is available also to
+      // code using the latest installed definition.
+      $definition_update_manager->updateEntityType($entity_type);
+
+      $storage_definition = BaseFieldDefinition::create('boolean')
+        ->setLabel(t('Default revision'))
+        ->setDescription(t('A flag indicating whether this was a default revision when it was saved.'))
+        ->setTranslatable(FALSE)
+        ->setRevisionable(TRUE)
+        // We cannot tell whether existing revisions were default or not when
+        // they were created, but since we did not support creating non-default
+        // revisions in any core stable UI so far, we default to TRUE.
+        ->setInitialValue(TRUE);
+
+      $definition_update_manager
+        ->installFieldStorageDefinition($field_name, $entity_type_id, $entity_type_id, $storage_definition);
+    }
+  }
+}
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
index fa55935bba..348c33cbb8 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
@@ -113,6 +113,7 @@ public function testEntityTypeUpdateWithoutData() {
         // The revision key is now defined, so the revision field needs to be
         // created.
         t('The %field_name field needs to be installed.', ['%field_name' => 'Revision ID']),
+        t('The %field_name field needs to be installed.', ['%field_name' => 'Default revision']),
       ],
     ];
     $this->assertEqual($this->entityDefinitionUpdateManager->getChangeSummary(), $expected, 'EntityDefinitionUpdateManager reports the expected change summary.');
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php b/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
index 73b3254630..3b9529ee6d 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
@@ -5,7 +5,6 @@
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\entity_test_revlog\Entity\EntityTestMulWithRevisionLog;
-use Drupal\KernelTests\KernelTestBase;
 use Drupal\user\Entity\User;
 use Drupal\user\UserInterface;
 
@@ -13,7 +12,7 @@
  * @coversDefaultClass \Drupal\Core\Entity\RevisionableContentEntityBase
  * @group Entity
  */
-class RevisionableContentEntityBaseTest extends KernelTestBase {
+class RevisionableContentEntityBaseTest extends EntityKernelTestBase {
 
   /**
    * {@inheritdoc}
@@ -25,10 +24,7 @@ class RevisionableContentEntityBaseTest extends KernelTestBase {
    */
   protected function setUp() {
     parent::setUp();
-
     $this->installEntitySchema('entity_test_mul_revlog');
-    $this->installEntitySchema('user');
-    $this->installSchema('system', 'sequences');
   }
 
   /**
@@ -89,6 +85,63 @@ public function testRevisionableContentEntity() {
     $this->assertItemsTableCount(3, $definition);
   }
 
+  /**
+   * Tests the behavior of the "revision_default" flag.
+   *
+   * @covers \Drupal\Core\Entity\ContentEntityBase::wasDefaultRevision
+   */
+  public function testWasDefaultRevision() {
+    $entity_type_id = 'entity_test_mul_revlog';
+    $entity = EntityTestMulWithRevisionLog::create([
+      'type' => $entity_type_id,
+    ]);
+
+    // Checks that in a new entity ::wasDefaultRevision() always matches
+    // ::isDefaultRevision().
+    $this->assertEquals($entity->isDefaultRevision(), $entity->wasDefaultRevision());
+    $entity->isDefaultRevision(FALSE);
+    $this->assertEquals($entity->isDefaultRevision(), $entity->wasDefaultRevision());
+
+    // Check that a new entity is always flagged as a default revision on save,
+    // regardless of its default revision status.
+    $entity->save();
+    $this->assertTrue($entity->wasDefaultRevision());
+
+    // Check that a pending revision is not flagged as default.
+    $entity->setNewRevision();
+    $entity->isDefaultRevision(FALSE);
+    $entity->save();
+    $this->assertFalse($entity->wasDefaultRevision());
+
+    // Check that a default revision is flagged as such.
+    $entity->setNewRevision();
+    $entity->isDefaultRevision(TRUE);
+    $entity->save();
+    $this->assertTrue($entity->wasDefaultRevision());
+
+    // Check that a manually set value for the "revision_default" flag is
+    // ignored on save.
+    $entity->setNewRevision();
+    $entity->isDefaultRevision(FALSE);
+    $entity->set('revision_default', TRUE);
+    $this->assertTrue($entity->wasDefaultRevision());
+    $entity->save();
+    $this->assertFalse($entity->wasDefaultRevision());
+
+    // Check that the default revision status was stored correctly.
+    $storage = $this->entityManager->getStorage($entity_type_id);
+    foreach ([TRUE, FALSE, TRUE, FALSE] as $index => $expected) {
+      /** @var \Drupal\entity_test_revlog\Entity\EntityTestMulWithRevisionLog $revision */
+      $revision = $storage->loadRevision($index + 1);
+      $this->assertEquals($expected, $revision->wasDefaultRevision());
+    }
+
+    // Check that the default revision is flagged correctly.
+    /** @var \Drupal\entity_test_revlog\Entity\EntityTestMulWithRevisionLog $entity */
+    $entity = $storage->loadUnchanged($entity->id());
+    $this->assertTrue($entity->wasDefaultRevision());
+  }
+
   /**
    * Asserts the ammount of items on entity related tables.
    *