diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5254fef11..4c07f008c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+* Post meta to log Outbox processing progress in the Outbox post type API endpoint.
+
 ### Fixed
 
 * Updates to certain user meta fields did not trigger an Update activity.
diff --git a/includes/class-activitypub.php b/includes/class-activitypub.php
index 0870d7613..b0e42012d 100644
--- a/includes/class-activitypub.php
+++ b/includes/class-activitypub.php
@@ -658,6 +658,35 @@ private static function register_post_types() {
 			)
 		);
 
+		\register_post_meta(
+			Outbox::POST_TYPE,
+			'_activitypub_outbox_processing',
+			array(
+				'type'         => 'object',
+				'single'       => true,
+				'description'  => 'Information about the processing of the outbox item.',
+				'show_in_rest' => array(
+					'schema' => array(
+						'type'       => 'object',
+						'properties' => array(
+							'started'       => array(
+								'type' => 'string',
+							),
+							'completed'     => array(
+								'type' => 'string',
+							),
+							'total_inboxes' => array(
+								'type' => 'integer',
+							),
+							'error_count'   => array(
+								'type' => 'integer',
+							),
+						),
+					),
+				),
+			)
+		);
+
 		// Both User and Blog Extra Fields types have the same args.
 		$args = array(
 			'labels'              => array(
diff --git a/includes/class-dispatcher.php b/includes/class-dispatcher.php
index 4ef43f886..78618c109 100644
--- a/includes/class-dispatcher.php
+++ b/includes/class-dispatcher.php
@@ -70,6 +70,9 @@ function ( $inboxes, $actor_id, $activity ) {
 			10,
 			3
 		);
+
+		\add_filter( 'activitypub_outbox_processing_complete', array( self::class, 'log_progress' ), 10, 7 );
+		\add_filter( 'activitypub_outbox_processing_batch_complete', array( self::class, 'log_progress' ), 10, 7 );
 	}
 
 	/**
@@ -142,10 +145,11 @@ public static function send_to_followers( $outbox_item_id, $batch_size = 50, $of
 			 * @param string $json           The ActivityPub Activity JSON
 			 * @param int    $actor_id       The actor ID.
 			 * @param int    $outbox_item_id The Outbox item ID.
+			 * @param array  $retries        The failed inboxes.
 			 * @param int    $batch_size     The batch size.
 			 * @param int    $offset         The offset.
 			 */
-			\do_action( 'activitypub_outbox_processing_complete', $inboxes, $json, $actor->get__id(), $outbox_item_id, $batch_size, $offset );
+			\do_action( 'activitypub_outbox_processing_complete', $inboxes, $json, $actor->get__id(), $outbox_item_id, $retries, $batch_size, $offset );
 
 			// No more followers to process for this update.
 			\wp_publish_post( $outbox_item_id );
@@ -159,10 +163,11 @@ public static function send_to_followers( $outbox_item_id, $batch_size = 50, $of
 			 * @param string $json           The ActivityPub Activity JSON
 			 * @param int    $actor_id       The actor ID.
 			 * @param int    $outbox_item_id The Outbox item ID.
+			 * @param array  $retries        The failed inboxes.
 			 * @param int    $batch_size     The batch size.
 			 * @param int    $offset         The offset.
 			 */
-			\do_action( 'activitypub_outbox_processing_batch_complete', $inboxes, $json, $actor->get__id(), $outbox_item_id, $batch_size, $offset );
+			\do_action( 'activitypub_outbox_processing_batch_complete', $inboxes, $json, $actor->get__id(), $outbox_item_id, $retries, $batch_size, $offset );
 
 			return array( $outbox_item_id, $batch_size, $offset + $batch_size );
 		}
@@ -355,6 +360,39 @@ public static function add_inboxes_of_replied_urls( $inboxes, $actor_id, $activi
 		return $inboxes;
 	}
 
+	/**
+	 * Track progress of outbox processing.
+	 *
+	 * @param array  $inboxes        The inboxes.
+	 * @param string $json           The ActivityPub Activity JSON.
+	 * @param int    $actor_id       The actor ID.
+	 * @param int    $outbox_item_id The Outbox item ID.
+	 * @param array  $retries        The failed inboxes.
+	 * @param int    $batch_size     The batch size.
+	 * @param int    $offset         The offset.
+	 */
+	public static function log_progress( $inboxes, $json, $actor_id, $outbox_item_id, $retries, $batch_size, $offset ) {
+		// Initialize processing data if this is the first batch.
+		if ( 0 === $offset ) {
+			$processing = array(
+				'started'       => current_time( 'mysql' ),
+				'total_inboxes' => 0,
+				'error_count'   => 0,
+			);
+		} else {
+			$processing = \get_post_meta( $outbox_item_id, '_activitypub_outbox_processing', true );
+		}
+
+		$processing['total_inboxes'] += count( $inboxes );
+		$processing['error_count']   += count( $retries );
+
+		if ( 'activitypub_outbox_processing_complete' === current_filter() ) {
+			$processing['completed'] = current_time( 'mysql' );
+		}
+
+		\update_post_meta( $outbox_item_id, '_activitypub_outbox_processing', $processing );
+	}
+
 	/**
 	 * Adds Blog Actor inboxes to Updates so the Blog User's followers are notified of edits.
 	 *
diff --git a/readme.txt b/readme.txt
index 6143c391c..d1ab56b6b 100644
--- a/readme.txt
+++ b/readme.txt
@@ -131,6 +131,7 @@ For reasons of data protection, it is not possible to see the followers of other
 
 = Unreleased =
 
+* Added: Post meta to log Outbox processing progress in the Outbox post type API endpoint.
 * Fixed: Updates to certain user meta fields did not trigger an Update activity.
 
 = 5.4.1 =