diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 6e7f66760f608..9832c8a2cf005 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -4711,7 +4711,7 @@ function get_post_galleries( $post, $html = true ) {
 		return array();
 	}
 
-	if ( ! has_shortcode( $post->post_content, 'gallery' ) ) {
+	if ( ! has_shortcode( $post->post_content, 'gallery' ) && ! has_block( 'gallery', $post->post_content ) ) {
 		return array();
 	}
 
@@ -4753,6 +4753,76 @@ function get_post_galleries( $post, $html = true ) {
 		}
 	}
 
+	if ( has_block( 'gallery', $post->post_content ) ) {
+		$post_blocks = parse_blocks( $post->post_content );
+		// Use while/array_shift instead of foreach so we can modify the array from within the loop
+		while ( $block = array_shift( $post_blocks ) ) {
+			if ( 'core/gallery' === $block['blockName'] ) {
+				// If a Gallery block has innerBlocks it is the new format and needs to be handled separately to the old
+				// format with nested <img> tags.
+				if ( ! empty( $block['innerBlocks'] ) ) {
+					$gallery_srcs = array();
+					$ids          = array();
+					$block_html   = array();
+					foreach ( $block['innerBlocks'] as $image ) {
+						if ( $html ) {
+							$block_html[] = $image['innerHTML'];
+						} else {
+							$gallery_srcs[] = wp_get_attachment_url( $image ['attrs']['id'] );
+							$ids[]          = $image['attrs']['id'];
+						}
+					}
+					if ( $html ) {
+						$galleries[] = '<figure>' . implode( ' ', $block_html ) . '</figure>';
+					} else {
+						$galleries[] = array(
+							// array_filter will eliminate any empty entries that came from unknown or invalid IDs
+							'src' => array_values( array_filter( array_unique( $gallery_srcs ) ) ),
+							// Only explicitly include the ids attribute. In future this could be changed to include all attributes, similar to $shortcode_attrs above.
+							'ids' => implode( ',', $ids ),
+						);
+					}
+				} else {
+					// Now handle the v1 gallery block format.
+					if ( $html ) {
+						$galleries[] = $block['innerHTML'];
+					} elseif ( ! empty( $block['attrs']['ids'] ) ) {
+						// Use the image IDs from the json blob as canonical if present
+						$gallery_srcs = array();
+						foreach ( $block['attrs']['ids'] as $gallery_img_id ) {
+							$gallery_srcs[] = wp_get_attachment_url( $gallery_img_id );
+						}
+						$galleries[] = array(
+							// array_filter will eliminate any empty entries that came from unknown or invalid IDs
+							'src' => array_values( array_filter( array_unique( $gallery_srcs ) ) ),
+							// Only explicitly include the ids attribute. In future this could be changed to include all attributes, similar to $shortcode_attrs above.
+							'ids' => implode( ',', $block['attrs']['ids'] ),
+						);
+					} else {
+						// Otherwise extract srcs from the innerHTML
+						$srcs = array();
+						preg_match_all( '#src=([\'"])(.+?)\1#is', $block['innerHTML'], $src, PREG_SET_ORDER );
+						if ( ! empty( $src ) ) {
+							foreach ( $src as $s ) {
+								$srcs[] = $s[2];
+							}
+						}
+
+						$galleries[] = array(
+							// Note that unlike shortcodes, all we are returning here is the src list
+							'src' => array_values( array_unique( $srcs ) ),
+						);
+					}
+				}
+			} elseif ( ! empty( $block['innerBlocks'] ) ) {
+				// If we have nested blocks then gradually flatten it by moving those onto the end of the root array for traversal
+				while ( $inner = array_pop( $block['innerBlocks'] ) ) {
+					array_push( $post_blocks, $inner );
+				}
+			}
+		}
+	}
+
 	/**
 	 * Filters the list of all found galleries in the given post.
 	 *
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 0483f0c0845d5..013e74851776d 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -510,9 +510,9 @@ public function test_get_attached_images() {
 	 * @ticket 22960
 	 */
 	public function test_post_galleries_images() {
-		$ids1      = array();
-		$ids1_srcs = array();
-		foreach ( range( 1, 3 ) as $i ) {
+		$ids      = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
 			$attachment_id = self::factory()->attachment->create_object(
 				"image$i.jpg",
 				0,
@@ -540,12 +540,12 @@ public function test_post_galleries_images() {
 			);
 			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
 			wp_update_attachment_metadata( $attachment_id, $metadata );
-			$ids2[]      = $attachment_id;
-			$ids2_srcs[] = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids[]      = $attachment_id;
+			$ids_srcs[] = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
 		}
 
-		$ids1_joined = implode( ',', $ids1 );
-		$ids2_joined = implode( ',', $ids2 );
+		$ids1_joined = join( ',', array_slice( $ids, 0, 3 ) );
+		$ids2_joined = join( ',', array_slice( $ids, 3, 3 ) );
 
 		$blob    = <<<BLOB
 [gallery ids="$ids1_joined"]
@@ -554,7 +554,7 @@ public function test_post_galleries_images() {
 BLOB;
 		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
 		$srcs    = get_post_galleries_images( $post_id );
-		$this->assertSame( $srcs, array( $ids1_srcs, $ids2_srcs ) );
+		$this->assertEquals( $srcs, array( array_slice( $ids_srcs, 0, 3 ), array_slice( $ids_srcs, 3, 3 ) ) );
 	}
 
 	/**
@@ -707,6 +707,354 @@ public function test_post_gallery_images() {
 		$this->assertSame( $srcs, $ids1_srcs );
 	}
 
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_block_post_galleries() {
+		// Set up an unattached image.
+		$this->factory->attachment->create_object(
+			array(
+				'file'           => 'test.jpg',
+				'post_parent'    => 0,
+				'post_mime_type' => 'image/jpeg',
+				'post_type'      => 'attachment',
+			)
+		);
+
+		$post_id = $this->factory->post->create(
+			array(
+				'post_content' => '<!-- wp:gallery -->',
+			)
+		);
+
+		$galleries = get_post_galleries( $post_id, false );
+
+		$this->assertTrue( is_array( $galleries ) );
+		$this->assertEmpty( $galleries[0]['src'] );
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_block_post_gallery_images() {
+		// Similar to test_post_gallery_images but with blocks instead of shortcodes
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids1[]      = $attachment_id;
+			$ids1_srcs[] = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids[]       = $attachment_id;
+			$url         = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[]  = $url;
+			$imgs[]      = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+
+		}
+
+		foreach ( range( 4, 6 ) as $i ) {
+			$imgs1_joined = join( "\n", array_slice( $imgs, 0, 3 ) );
+			$imgs2_joined = join( "\n", array_slice( $imgs, 3, 3 ) );
+		}
+		$blob    = <<<BLOB
+<!-- wp:gallery -->
+$imgs1_joined
+<!-- /wp:gallery -->
+<!-- wp:gallery -->
+$imgs2_joined
+<!-- /wp:gallery -->
+BLOB;
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+		$srcs    = get_post_gallery_images( $post_id );
+		$this->assertEquals( $srcs, array_slice( $ids_srcs, 0, 3 ) );
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_block_post_gallery_images_json() {
+		// Similar to test_block_post_gallery_images, with IDs in the json blob
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+
+		}
+
+		$ids1_joined = join( ',', array_slice( $ids, 0, 3 ) );
+		$ids2_joined = join( ',', array_slice( $ids, 3, 3 ) );
+
+		$blob    = <<<BLOB
+<!-- wp:gallery {"ids":[$ids1_joined]} -->
+<!-- /wp:gallery -->
+
+<!-- wp:gallery {"ids":[$ids2_joined]} -->
+<!-- /wp:gallery -->
+BLOB;
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+		$srcs    = get_post_gallery_images( $post_id );
+		$this->assertEquals( $srcs, array_slice( $ids_srcs, 0, 3 ) );
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_mixed_post_gallery_images() {
+		// Similar to test_post_gallery_images but with a shortcode and a block in the same post
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0,
+				array(
+					'post_mime_type' => 'image/jpeg',
+					'post_type'      => 'attachment',
+				)
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+		}
+
+		$ids1_joined  = join( "\n", array_slice( $ids, 0, 3 ) );
+		$ids2_joined  = join( "\n", array_slice( $ids, 3, 3 ) );
+		$imgs2_joined = join( "\n", array_slice( $imgs, 3, 3 ) );
+
+		$blob    = <<<BLOB
+[gallery ids="$ids1_joined"]
+
+[gallery ids="$ids2_joined"]
+<!-- wp:gallery -->
+$imgs2_joined
+<!-- /wp:gallery -->
+BLOB;
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+		$srcs    = get_post_gallery_images( $post_id );
+		$this->assertEquals( $srcs, array_slice( $ids_srcs, 0, 3 ) );
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_mixed_post_galleries() {
+		// Test the get_post_galleries() function in $html=false mode, with both shortcode and block galleries
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0,
+				array(
+					'post_mime_type' => 'image/jpeg',
+					'post_type'      => 'attachment',
+				)
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+
+		}
+
+		$ids1_joined = join( ',', array_slice( $ids, 0, 3 ) );
+		$ids2_joined = join( ',', array_slice( $ids, 3, 3 ) );
+
+		$blob = <<<BLOB
+[gallery ids="$ids1_joined"]
+
+<!-- wp:gallery {"ids":[$ids2_joined]} -->
+<!-- /wp:gallery -->
+BLOB;
+
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+
+		$galleries = get_post_galleries( $post_id, false );
+		$this->assertEquals(
+			$galleries,
+			array(
+				array(
+					'ids' => $ids1_joined,
+					'src' => array_slice( $ids_srcs, 0, 3 ),
+				),
+				array(
+					'ids' => $ids2_joined,
+					'src' => array_slice( $ids_srcs, 3, 3 ),
+				),
+			)
+		);
+
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_mixed_post_galleries_data() {
+		// Test attributes returned by get_post_galleries() function in $html=false mode, with both shortcode and block galleries
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 6 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0,
+				array(
+					'post_mime_type' => 'image/jpeg',
+					'post_type'      => 'attachment',
+				)
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+
+		}
+
+		$ids1_joined = join( ',', array_slice( $ids, 0, 3 ) );
+		$ids2_joined = join( ',', array_slice( $ids, 3, 3 ) );
+		$blob        = <<<BLOB
+[gallery ids="$ids1_joined" type="type" foo="bar"]
+
+<!-- wp:gallery {"ids":[$ids2_joined],"columns":3,"imageCrop":false,"linkTo":"media"} -->
+<!-- /wp:gallery -->
+BLOB;
+
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+
+		$galleries = get_post_galleries( $post_id, false );
+		$this->assertEquals(
+			$galleries,
+			array(
+				array(
+					'ids'  => $ids1_joined,
+					'src'  => array_slice( $ids_srcs, 0, 3 ),
+					'type' => 'type',
+					'foo'  => 'bar', // The shortcode code passes arbitrary attributes
+				),
+				array(
+					'ids' => $ids2_joined,
+					'src' => array_slice( $ids_srcs, 3, 3 ),
+					// The block only passes ids, no other attributes
+				),
+			)
+		);
+
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_block_inner_post_gallery_images() {
+		// Make sure get_post_gallery_images() works with gallery blocks that are nested inside something else
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 3 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0,
+				array(
+					'post_mime_type' => 'image/jpeg',
+					'post_type'      => 'attachment',
+				)
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<figure><img src="' . $url . '" data-id="' . $i . '" /></figure>';
+
+		}
+
+		$imgs_joined = join( "\n", $imgs );
+
+		$blob    = <<<BLOB
+<!-- wp:columns -->
+<!-- wp:column -->
+<!-- wp:gallery -->
+$imgs_joined
+<!-- /wp:gallery -->
+<!-- /wp:column -->
+<!-- /wp:columns -->
+BLOB;
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+		$srcs    = get_post_gallery_images( $post_id );
+		$this->assertEquals( $srcs, $ids_srcs );
+	}
+
+	/**
+	 * @ticket 43826
+	 * @group blocks
+	 */
+	public function test_block_post_gallery_innerblock_images() {
+		// Make sure get_post_gallery_images() works with new version of gallery block with nested image blocks.
+		$ids      = array();
+		$imgs     = array();
+		$ids_srcs = array();
+		foreach ( range( 1, 3 ) as $i ) {
+			$attachment_id = self::factory()->attachment->create_object(
+				"image$i.jpg",
+				0,
+				array(
+					'post_mime_type' => 'image/jpeg',
+					'post_type'      => 'attachment',
+				)
+			);
+			$metadata      = array_merge( array( 'file' => "image$i.jpg" ), $this->img_meta );
+			wp_update_attachment_metadata( $attachment_id, $metadata );
+			$ids[]      = $attachment_id;
+			$url        = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . "image$i.jpg";
+			$ids_srcs[] = $url;
+			$imgs[]     = '<!-- wp:image {"id":' . $attachment_id . ',"sizeSlug":"large","linkDestination":"none"} --><figure class="wp-block-image size-large"><img src="' . $url . '" /></figure><!-- /wp:image -->';
+
+		}
+
+		$imgs_joined = join( "\n", $imgs );
+
+		$blob    = <<<BLOB
+<!-- wp:gallery -->
+<figure class="wp-block-gallery has-nested-images columns-default is-cropped">
+$imgs_joined
+</figure>
+<!-- /wp:gallery -->
+BLOB;
+		$post_id = self::factory()->post->create( array( 'post_content' => $blob ) );
+		$srcs    = get_post_gallery_images( $post_id );
+		$this->assertEquals( $srcs, $ids_srcs );
+	}
+
 	public function test_get_media_embedded_in_content() {
 		$object = <<<OBJ
 <object src="this" data="that">