diff --git a/media_entity.module b/media_entity.module
index d54f773..9b157e5 100644
--- a/media_entity.module
+++ b/media_entity.module
@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\media_entity\Entity\MediaBundle;
 
 /**
  * Implements hook_help().
diff --git a/src/Entity/MediaBundle.php b/src/Entity/MediaBundle.php
index 8833f82..277f53a 100644
--- a/src/Entity/MediaBundle.php
+++ b/src/Entity/MediaBundle.php
@@ -2,12 +2,14 @@
 
 namespace Drupal\media_entity\Entity;
 
-use Drupal\Core\Entity\EntityDescriptionInterface;
 use Drupal\Core\Config\Entity\ConfigEntityBundleBase;
+use Drupal\Core\Entity\EntityDescriptionInterface;
+use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\EntityWithPluginCollectionInterface;
 use Drupal\Core\Plugin\DefaultSingleLazyPluginCollection;
 use Drupal\media_entity\MediaBundleInterface;
 use Drupal\media_entity\MediaInterface;
+use Drupal\field\Entity\FieldConfig;
 
 /**
  * Defines the Media bundle configuration entity.
@@ -44,6 +46,7 @@ use Drupal\media_entity\MediaInterface;
  *     "type_configuration",
  *     "field_map",
  *     "status",
+ *     "create_source_field",
  *   },
  *   links = {
  *     "add-form" = "/admin/structure/media/add",
@@ -121,7 +124,7 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
   /**
    * Default status of this media bundle.
    *
-   * @var array
+   * @var bool
    */
   public $status = TRUE;
 
@@ -241,4 +244,48 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
     $this->new_revision = $new_revision;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
+    parent::postSave($storage, $update);
+
+    if (!$update) {
+      // When creating new bundles, add also a source field, if configured to
+      // do so.
+      if (!$this->isSyncing() && empty($this->getTypeConfiguration()['source_field']) && !empty($this->getTypeConfiguration()['create_source_field'])) {
+        $media_type_manager = \Drupal::service('plugin.manager.media_entity.type');
+        /** @var \Drupal\media_entity\MediaTypeInterface $instance */
+        $instance = $media_type_manager->createInstance($this->getType()->getPluginId(), $this->getTypeConfiguration());
+        $default_field = $instance->getDefaultSourceField();
+
+        if (!empty($default_field['storage'])) {
+          // Save the field storage and create the instance.
+          $default_field['storage']->save();
+          FieldConfig::create([
+            'entity_type' => 'media',
+            'field_name' => $default_field['field_name'],
+            'label' => $default_field['label'],
+            'required' => TRUE,
+            'bundle' => $this->id(),
+          ])->save();
+
+          // Make the field visible on the form display.
+          $form_display = entity_get_form_display('media', $this->id(), 'default');
+          $form_display->setComponent($default_field['field_name'], [
+            'type' => $default_field['field_widget'],
+          ])->save();
+
+          // Make the field visible on the media entity itself.
+          $display = entity_get_display('media', $this->id(), 'default');
+          $display->setComponent($default_field['field_name'], [
+            'type' => $default_field['field_formatter'],
+          ])->save();
+        }
+
+      }
+    }
+
+  }
+
 }
diff --git a/src/MediaBundleForm.php b/src/MediaBundleForm.php
index 36365f3..6ae83bb 100644
--- a/src/MediaBundleForm.php
+++ b/src/MediaBundleForm.php
@@ -313,6 +313,14 @@ class MediaBundleForm extends EntityForm {
     $plugin_configuration = !empty($this->configurableInstances[$plugin]['plugin_config']) ? $this->configurableInstances[$plugin]['plugin_config'] : [];
     $instance = $this->mediaTypeManager->createInstance($plugin, $plugin_configuration);
     $instance->submitConfigurationForm($form, $form_state);
+
+    // Save the flag to auto-create a source field.
+    $this->entity->create_source_field = $form_state->getValue([
+      'type_configuration',
+      $plugin,
+      'create_source_field',
+    ]);
+
   }
 
   /**
diff --git a/src/MediaTypeBase.php b/src/MediaTypeBase.php
index a472e7d..0041851 100644
--- a/src/MediaTypeBase.php
+++ b/src/MediaTypeBase.php
@@ -3,14 +3,14 @@
 namespace Drupal\media_entity;
 
 use Drupal\Component\Plugin\PluginBase;
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Config\Config;
 use Drupal\Core\Entity\EntityFieldManagerInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
-use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
-use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Base implementation of media type plugin.
@@ -158,4 +158,11 @@ abstract class MediaTypeBase extends PluginBase implements MediaTypeInterface, C
     return 'media:' . $media->bundle() . ':' . $media->uuid();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getDefaultSourceField() {
+    return [];
+  }
+
 }
diff --git a/src/MediaTypeInterface.php b/src/MediaTypeInterface.php
index 2a171c2..32a49e5 100644
--- a/src/MediaTypeInterface.php
+++ b/src/MediaTypeInterface.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\media_entity;
 
-use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Component\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Core\Plugin\PluginFormInterface;
 
 /**
@@ -85,4 +85,26 @@ interface MediaTypeInterface extends PluginInspectionInterface, ConfigurablePlug
    */
   public function getDefaultName(MediaInterface $media);
 
+  /**
+   * Provide a default source field.
+   *
+   * Plugins defining media bundles are suggested to implement this method and
+   * create a field that will be used as default source field, on bundle
+   * creation. Make sure this method returns unsaved entities, once these are
+   * only going to be saved and used if the user marked the option to use the
+   * default field provided.
+   *
+   * @return array
+   *   An associative array containing the following keys:
+   *   'storage' => \Drupal\field\Entity\FieldStorageConfig A config entity for
+   *   this field storage.
+   *   'field_name' => (string) The name to be used for the field instance.
+   *   'label' => (string) The label to be used for the field instance.
+   *   'field_widget' => (string) The id of the widget to use.
+   *   'field_formatter' => (string) The id of the formatter to use.
+   *   Note that the storage config entity need to be returned unsaved, and the
+   *   main form will be responsible for saving them.
+   */
+  public function getDefaultSourceField();
+
 }