diff --git a/src/Metadata/class-metadata-builder.php b/src/Metadata/class-metadata-builder.php
index 99959862f..2a74af1ee 100644
--- a/src/Metadata/class-metadata-builder.php
+++ b/src/Metadata/class-metadata-builder.php
@@ -119,6 +119,21 @@ protected function build_type( WP_Post $post, string $parsely_type ): void {
 		$this->metadata['@type'] = $type;
 	}
 
+	/**
+	 * Populates the custom metadata field with the current post's/page's ID.
+	 *
+	 * @since 3.16.0
+	 *
+	 * @param WP_Post $post The post/page for which to populate the field.
+	 */
+	protected function build_post_id( WP_Post $post ): void {
+		$this->metadata['custom_metadata'] = wp_json_encode(
+			array(
+				'wpParselyPostID' => $post->ID,
+			)
+		);
+	}
+
 	/**
 	 * Populates the mainEntityOfPage field in the metadata object.
 	 *
diff --git a/src/Metadata/class-post-builder.php b/src/Metadata/class-post-builder.php
index 8f1746684..a92ecf3ee 100644
--- a/src/Metadata/class-post-builder.php
+++ b/src/Metadata/class-post-builder.php
@@ -60,6 +60,7 @@ public function get_metadata(): array {
 		$this->build_publisher();
 		$this->build_keywords( $this->post );
 		$this->build_metadata_post_times( $this->post );
+		$this->build_post_id( $this->post );
 
 		return $this->metadata;
 	}
diff --git a/tests/Integration/Endpoints/RestMetadataTest.php b/tests/Integration/Endpoints/RestMetadataTest.php
index 23854b34c..a449947a3 100644
--- a/tests/Integration/Endpoints/RestMetadataTest.php
+++ b/tests/Integration/Endpoints/RestMetadataTest.php
@@ -403,7 +403,8 @@ public function test_get_rendered_meta_json_ld(): void {
 		$this->go_to( (string) $this->get_permalink( $post_id ) );
 
 		$meta_string = self::$rest->get_rendered_meta( 'json_ld' );
-		$expected    = '<script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"NewsArticle","headline":"My test_get_rendered_meta_json_ld title","url":"http:\/\/example.org\/?p=' . $post_id . '","mainEntityOfPage":{"@type":"WebPage","@id":"http:\/\/example.org\/?p=' . $post_id . '"},"thumbnailUrl":"","image":{"@type":"ImageObject","url":""},"articleSection":"Uncategorized","author":[],"creator":[],"publisher":{"@type":"Organization","name":"Test Blog","logo":""},"keywords":[],"dateCreated":"' . $date . '","datePublished":"' . $date . '","dateModified":"' . $date . '"}</script>';
+		$expected    = '<script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"NewsArticle","headline":"My test_get_rendered_meta_json_ld title","url":"http:\/\/example.org\/?p=' . $post_id . '","mainEntityOfPage":{"@type":"WebPage","@id":"http:\/\/example.org\/?p=' . $post_id . '"},"thumbnailUrl":"","image":{"@type":"ImageObject","url":""},"articleSection":"Uncategorized","author":[],"creator":[],"publisher":{"@type":"Organization","name":"Test Blog","logo":""},"keywords":[],"dateCreated":"' . $date . '","datePublished":"' . $date . '","dateModified":"' . $date . '","custom_metadata":"{\\"wpParselyPostID\\":' . $post_id . '}"}</script>' .
+			'<meta name="parsely-metadata" content="{&quot;wpParselyPostID&quot;:' . $post_id . '}" />';
 		self::assertSame( $expected, $meta_string );
 	}
 
@@ -471,7 +472,8 @@ public function test_get_rendered_repeated_metas(): void {
 <meta name="parsely-link" content="http://example.org/?p=' . $post_id . '" />
 <meta name="parsely-type" content="post" />
 <meta name="parsely-pub-date" content="' . $date . '" />
-<meta name="parsely-section" content="Uncategorized" />';
+<meta name="parsely-section" content="Uncategorized" />
+<meta name="parsely-metadata" content="{&quot;wpParselyPostID&quot;:' . $post_id . '}" />';
 		self::assertSame( $expected, $meta_string );
 	}