diff --git a/core/modules/media/src/Entity/Media.php b/core/modules/media/src/Entity/Media.php
index 9c389235ab..e6538a4706 100644
--- a/core/modules/media/src/Entity/Media.php
+++ b/core/modules/media/src/Entity/Media.php
@@ -10,6 +10,8 @@
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\media\MediaInterface;
 use Drupal\Core\Entity\EntityChangedTrait;
+use Drupal\media\MediaSourceEntityConstraintsInterface;
+use Drupal\media\MediaSourceFieldConstraintsInterface;
 use Drupal\user\UserInterface;
 
 /**
@@ -255,6 +257,11 @@ protected function shouldUpdateThumbnail($is_new = FALSE) {
    * {@inheritdoc}
    */
   public function preSave(EntityStorageInterface $storage) {
+    // If the source plugin defines any constraints we enforce the validation.
+    if ($this->getSource() instanceof MediaSourceEntityConstraintsInterface || $this->getSource() instanceof MediaSourceFieldConstraintsInterface) {
+      $this->setValidationRequired(TRUE);
+    }
+
     parent::preSave($storage);
 
     // Try to set fields provided by the media source and mapped in
diff --git a/core/modules/media/src/MediaSourceBase.php b/core/modules/media/src/MediaSourceBase.php
index 2f117b066a..aa911c69b6 100644
--- a/core/modules/media/src/MediaSourceBase.php
+++ b/core/modules/media/src/MediaSourceBase.php
@@ -239,6 +239,7 @@ protected function createSourceFieldStorage() {
         'entity_type' => 'media',
         'field_name' => $this->getSourceFieldName(),
         'type' => reset($this->pluginDefinition['allowed_field_types']),
+        'locked' => TRUE,
       ]);
   }
 
diff --git a/core/modules/media/src/MediaSourceEntityConstraintsInterface.php b/core/modules/media/src/MediaSourceEntityConstraintsInterface.php
new file mode 100644
index 0000000000..b62890fda7
--- /dev/null
+++ b/core/modules/media/src/MediaSourceEntityConstraintsInterface.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\media;
+
+/**
+ * Defines a interface for a media source with entity constraints.
+ *
+ * This allows a media source to optionally add entity validation constraints
+ * for media items. To add contraints at source field level a media source
+ * can also implement MediaSourceFieldConstraintsInterface.
+ *
+ * @see \Drupal\media\MediaSourceInterface
+ * @see \Drupal\media\MediaSourceFieldConstraintsInterface.php
+ * @see \Drupal\media\MediaSourceBase
+ * @see \Drupal\media\Entity\Media
+ */
+interface MediaSourceEntityConstraintsInterface extends MediaSourceInterface {
+
+  /**
+   * Gets media source-specific validation constraints for a media item.
+   *
+   * @return \Symfony\Component\Validator\Constraint[]
+   *   An array of validation constraint definitions, keyed by constraint name.
+   *   Each constraint definition can be used for instantiating
+   *   \Symfony\Component\Validator\Constraint objects.
+   */
+  public function getEntityConstraints();
+
+}
diff --git a/core/modules/media/src/MediaSourceFieldConstraintsInterface.php b/core/modules/media/src/MediaSourceFieldConstraintsInterface.php
new file mode 100644
index 0000000000..37c74c3080
--- /dev/null
+++ b/core/modules/media/src/MediaSourceFieldConstraintsInterface.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\media;
+
+/**
+ * Defines a interface for a media source with source field constraints.
+ *
+ * This allows a media source to optionally add source field validation
+ * constraints for media items. To add contraints at entity level a
+ * media source can also implement MediaSourceEntityConstraintsInterface.
+ *
+ * @see \Drupal\media\MediaSourceInterface
+ * @see \Drupal\media\MediaSourceEntityConstraintsInterface
+ * @see \Drupal\media\MediaSourceBase
+ * @see \Drupal\media\Entity\Media
+ */
+interface MediaSourceFieldConstraintsInterface extends MediaSourceInterface {
+
+  /**
+   * Gets media source-specific validation constraints for a source field.
+   *
+   * @return \Symfony\Component\Validator\Constraint[]
+   *   An array of validation constraint definitions, keyed by constraint name.
+   *   Each constraint definition can be used for instantiating
+   *   \Symfony\Component\Validator\Constraint objects.
+   */
+  public function getSourceFieldConstraints();
+
+}
diff --git a/core/modules/media/tests/modules/media_test_source/config/schema/media_test_source.schema.yml b/core/modules/media/tests/modules/media_test_source/config/schema/media_test_source.schema.yml
index b04dec6e5a..25d6bfbcdf 100644
--- a/core/modules/media/tests/modules/media_test_source/config/schema/media_test_source.schema.yml
+++ b/core/modules/media/tests/modules/media_test_source/config/schema/media_test_source.schema.yml
@@ -5,3 +5,7 @@ media.source.test:
     test_config_value:
       type: string
       label: 'Test config value'
+
+media.source.test_constraints:
+  type: media.source.test
+  label: 'Test media source with constraints configuration'
diff --git a/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraint.php b/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraint.php
new file mode 100644
index 0000000000..4144cec2fa
--- /dev/null
+++ b/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraint.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Drupal\media_test_source\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Checks if a value is a valid Tweet embed code/URL.
+ *
+ * @Constraint(
+ *   id = "MediaTestConstraint",
+ *   label = @Translation("Media constraint for test purposes.", context = "Validation"),
+ *   type = { "entity", "string" }
+ * )
+ */
+class MediaTestConstraint extends Constraint {
+
+  /**
+   * The default violation message.
+   *
+   * @var string
+   */
+  public $message = 'Inappropriate text.';
+
+}
diff --git a/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraintValidator.php b/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraintValidator.php
new file mode 100644
index 0000000000..1c744430a5
--- /dev/null
+++ b/core/modules/media/tests/modules/media_test_source/src/Plugin/Validation/Constraint/MediaTestConstraintValidator.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\media_test_source\Plugin\Validation\Constraint;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the MediaTestConstraint.
+ */
+class MediaTestConstraintValidator extends ConstraintValidator {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($value, Constraint $constraint) {
+    if ($value instanceof EntityInterface) {
+      $string_to_test = $value->label();
+    }
+    elseif ($value instanceof FieldItemListInterface) {
+      $string_to_test = $value->value;
+    }
+    else {
+      return;
+    }
+
+    if (strpos($string_to_test, 'love Drupal') === FALSE) {
+      $this->context->addViolation($constraint->message);
+    }
+  }
+
+}
diff --git a/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestWithConstraints.php b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestWithConstraints.php
new file mode 100644
index 0000000000..98039ca2d2
--- /dev/null
+++ b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestWithConstraints.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\media_test_source\Plugin\media\Source;
+
+use Drupal\media\MediaSourceEntityConstraintsInterface;
+use Drupal\media\MediaSourceFieldConstraintsInterface;
+
+/**
+ * Provides generic media type.
+ *
+ * @MediaSource(
+ *   id = "test_constraints",
+ *   label = @Translation("Test source with constraints"),
+ *   description = @Translation("Test media source that provides constraints."),
+ *   allowed_field_types = {"string_long"},
+ * )
+ */
+class TestWithConstraints extends Test implements MediaSourceEntityConstraintsInterface, MediaSourceFieldConstraintsInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getEntityConstraints() {
+    return \Drupal::state()->get('media_source_test_entity_constraints', []);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getSourceFieldConstraints() {
+    return \Drupal::state()->get('media_source_test_field_constraints', []);
+  }
+
+}
diff --git a/core/modules/media/tests/src/Kernel/MediaKernelTestBase.php b/core/modules/media/tests/src/Kernel/MediaKernelTestBase.php
index e13150e0ff..ffc4224b56 100644
--- a/core/modules/media/tests/src/Kernel/MediaKernelTestBase.php
+++ b/core/modules/media/tests/src/Kernel/MediaKernelTestBase.php
@@ -33,6 +33,13 @@
   protected $testMediaType;
 
   /**
+   * The test media type with constraints.
+   *
+   * @var \Drupal\media\MediaTypeInterface
+   */
+  protected $testConstraintsMediaType;
+
+  /**
    * {@inheritdoc}
    */
   protected function setUp() {
@@ -53,14 +60,28 @@ protected function setUp() {
       'new_revision' => FALSE,
     ]);
     $this->testMediaType->save();
-
     $source_field = $this->testMediaType->getSource()->createSourceField($this->testMediaType);
     $source_field->getFieldStorageDefinition()->save();
     $source_field->save();
-
     $this->testMediaType->set('source_configuration', [
       'source_field' => $source_field->getName(),
     ])->save();
+
+    // Create a test media type with constraints.
+    $id = strtolower($this->randomMachineName());
+    $this->testConstraintsMediaType = MediaType::create([
+      'id' => $id,
+      'label' => $id,
+      'source' => 'test_constraints',
+      'new_revision' => FALSE,
+    ]);
+    $this->testConstraintsMediaType->save();
+    $source_field = $this->testConstraintsMediaType->getSource()->createSourceField($this->testConstraintsMediaType);
+    $source_field->getFieldStorageDefinition()->save();
+    $source_field->save();
+    $this->testConstraintsMediaType->set('source_configuration', [
+      'source_field' => $source_field->getName(),
+    ])->save();
   }
 
 }
diff --git a/core/modules/media/tests/src/Kernel/MediaSourceTest.php b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
index 14349c69aa..f6b4a69514 100644
--- a/core/modules/media/tests/src/Kernel/MediaSourceTest.php
+++ b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
@@ -2,7 +2,9 @@
 
 namespace Drupal\Tests\media\Kernel;
 
+use Drupal\Core\Entity\EntityStorageException;
 use Drupal\media\Entity\Media;
+use Drupal\media\Entity\MediaType;
 
 /**
  * Tests media source plugins related logic.
@@ -228,4 +230,154 @@ public function testThumbnail() {
     $this->assertEquals('This will be title.', $media->thumbnail->title, 'Title text was set on the thumbnail.');
     $this->assertEquals('This will be alt.', $media->thumbnail->alt, 'Alt text was set on the thumbnail.');
   }
+
+  /**
+   * Tests the media entity constraints functionality.
+   */
+  public function testConstraints() {
+    // Test entity constraints.
+    \Drupal::state()->set('media_source_test_entity_constraints', [
+      'MediaTestConstraint' => [],
+    ]);
+
+    // Create media that uses source with constraints and make sure it can't
+    // be saved without validating them.
+    /** @var \Drupal\media\MediaInterface $media */
+    $media = Media::create([
+      'bundle' => $this->testConstraintsMediaType->id(),
+      'name' => 'I do not like Drupal',
+      'field_media_test_constraints' => 'Not checked',
+    ]);
+    try {
+      $media->save();
+      $this->fail('Save was allowed without validation.');
+    }
+    catch (EntityStorageException $exception) {
+      $this->assertTrue(TRUE, 'Validation was enforced before save.');
+    }
+
+    // Validate the entity and make sure violation is reported.
+    /** @var \Drupal\Core\Entity\EntityConstraintViolationListInterface $violations */
+    $violations = $media->validate();
+    $this->assertEquals(1, $violations->count(), 'Expected number of validations found.');
+    $this->assertEquals('Inappropriate text.', $violations->get(0)->getMessage(), 'Correct constraint validation message found.');
+
+    // Fix the violation and make sure it is not reported anymore.
+    $media->set('name', 'I love Drupal!');
+    $violations = $media->validate();
+    $this->assertEquals(0, $violations->count(), 'Expected number of validations found.');
+
+    // Save and make sure it succeeded.
+    $this->assertEmpty($media->id(), 'Entity ID was not found.');
+    $media->save();
+    $this->assertNotEmpty($media->id(), 'Entity ID was found.');
+
+    // Test source field constraints.
+    \Drupal::state()->set('media_source_test_field_constraints', [
+      'MediaTestConstraint' => [],
+    ]);
+    \Drupal::state()->set('media_source_test_entity_constraints', []);
+
+    // Create media that uses source with constraints and make sure it can't
+    // be saved without validating them.
+    /** @var \Drupal\media\MediaInterface $media */
+    $media = Media::create([
+      'bundle' => $this->testConstraintsMediaType->id(),
+      'name' => 'Not checked',
+      'field_media_test_constraints' => 'I do not like Drupal',
+    ]);
+    try {
+      $media->save();
+      $this->fail('Save was allowed without validation.');
+    }
+    catch (EntityStorageException $exception) {
+      $this->assertTrue(TRUE, 'Validation was enforced before save.');
+    }
+
+    // Validate the entity and make sure violation is reported.
+    /** @var \Drupal\Core\Entity\EntityConstraintViolationListInterface $violations */
+    $violations = $media->validate();
+    $this->assertEquals(1, $violations->count(), 'Expected number of validations found.');
+    $this->assertEquals('Inappropriate text.', $violations->get(0)->getMessage(), 'Correct constraint validation message found.');
+
+    // Fix the violation and make sure it is not reported anymore.
+    $media->set('field_media_test_constraints', 'I love Drupal!');
+    $violations = $media->validate();
+    $this->assertEquals(0, $violations->count(), 'Expected number of validations found.');
+
+    // Save and make sure it succeeded.
+    $this->assertEmpty($media->id(), 'Entity ID was not found.');
+    $media->save();
+    $this->assertNotEmpty($media->id(), 'Entity ID was found.');
+  }
+
+  /**
+   * Tests logic related to the automated source field creation.
+   */
+  public function testSourceFieldCreation() {
+    /** @var \Drupal\media\MediaTypeInterface $type */
+    $type = MediaType::create([
+      'id' => 'test_type',
+      'label' => 'Test type',
+      'source' => 'test',
+    ]);
+
+    /** @var \Drupal\field\Entity\FieldConfig $field */
+    $field = $type->getSource()->createSourceField($type);
+    /** @var \Drupal\field\Entity\FieldStorageConfig $field_storage */
+    $field_storage = $field->getFieldStorageDefinition();
+
+    // Test field storage.
+    $this->assertTrue($field_storage->isNew(), 'Field storage is not saved automatically.');
+    $this->assertTrue($field_storage->isLocked(), 'Field storage is locked.');
+    $this->assertEquals('string', $field_storage->getType(), 'Field is of correct type.');
+    $this->assertEquals('field_media_test_1', $field_storage->getName(), 'Correct field name is used.');
+    $this->assertEquals('media', $field_storage->getTargetEntityTypeId(), 'Field is targeting media entities.');
+
+    // Test field.
+    $this->assertTrue($field->isNew(), 'Field is not saved automatically.');
+    $this->assertEquals('field_media_test_1', $field->getName(), 'Correct field name is used.');
+    $this->assertEquals('string', $field->getType(), 'Field is of correct type.');
+    $this->assertTrue($field->isRequired(), 'Field is required.');
+    $this->assertEquals('Test source', $field->label(), 'Correct label is used.');
+    $this->assertEquals('test_type', $field->getTargetBundle(), 'Field is targeting correct bundle.');
+
+    // Fields should be automatically saved only when using a form.
+    // Drupal\Tests\media\FunctionalJavascript\MediaTypeCreationTest is testing
+    // form part of the functionality.
+    $type->save();
+    $storage = $this->container->get('entity_type.manager')
+      ->getStorage('field_storage_config')
+      ->load('media.field_media_test_1');
+    $this->assertNull($storage, 'Field storage was not saved.');
+    $field = $this->container->get('entity_type.manager')
+      ->getStorage('field_config')
+      ->load('media.test_type.field_media_test_1');
+    $this->assertNull($field, 'Field storage was not saved.');
+
+    // Test the plugin with a different default source field type.
+    $type = MediaType::create([
+      'id' => 'test_constraints_type',
+      'label' => 'Test type with constraints',
+      'source' => 'test_constraints',
+    ]);
+    $field = $type->getSource()->createSourceField($type);
+    $field_storage = $field->getFieldStorageDefinition();
+
+    // Test field storage.
+    $this->assertTrue($field_storage->isNew(), 'Field storage is not saved automatically.');
+    $this->assertTrue($field_storage->isLocked(), 'Field storage is locked.');
+    $this->assertEquals('string_long', $field_storage->getType(), 'Field is of correct type.');
+    $this->assertEquals('field_media_test_constraints_1', $field_storage->getName(), 'Correct field name is used.');
+    $this->assertEquals('media', $field_storage->getTargetEntityTypeId(), 'Field is targeting media entities.');
+
+    // Test field.
+    $this->assertTrue($field->isNew(), 'Field is not saved automatically.');
+    $this->assertEquals('field_media_test_constraints_1', $field->getName(), 'Correct field name is used.');
+    $this->assertEquals('string_long', $field->getType(), 'Field is of correct type.');
+    $this->assertTrue($field->isRequired(), 'Field is required.');
+    $this->assertEquals('Test source with constraints', $field->label(), 'Correct label is used.');
+    $this->assertEquals('test_constraints_type', $field->getTargetBundle(), 'Field is targeting correct bundle.');
+  }
+
 }