diff --git a/docs/reference-guides/core-blocks.md b/docs/reference-guides/core-blocks.md
index 7e359ae4bc747..e3601a1f0a509 100644
--- a/docs/reference-guides/core-blocks.md
+++ b/docs/reference-guides/core-blocks.md
@@ -284,7 +284,7 @@ Introduce new sections and organize content to help visitors (and search engines
 
 -	**Name:** core/heading
 -	**Category:** text
--	**Supports:** __unstablePasteTextInline, align (full, wide), anchor, color (background, gradients, link, text), spacing (margin, padding), typography (fontSize, lineHeight), ~~className~~
+-	**Supports:** __unstablePasteTextInline, align (full, wide), anchor, className, color (background, gradients, link, text), spacing (margin, padding), typography (fontSize, lineHeight)
 -	**Attributes:** content, level, placeholder, textAlign
 
 ## Home Link
diff --git a/lib/blocks.php b/lib/blocks.php
index 669decebf2c36..add72e77062cb 100644
--- a/lib/blocks.php
+++ b/lib/blocks.php
@@ -23,7 +23,6 @@ function gutenberg_reregister_core_block_types() {
 				'columns',
 				'comments',
 				'group',
-				'heading',
 				'html',
 				'list',
 				'list-item',
@@ -69,6 +68,7 @@ function gutenberg_reregister_core_block_types() {
 				'home-link.php'                    => 'core/home-link',
 				'image.php'                        => 'core/image',
 				'gallery.php'                      => 'core/gallery',
+				'heading.php'                      => 'core/heading',
 				'latest-comments.php'              => 'core/latest-comments',
 				'latest-posts.php'                 => 'core/latest-posts',
 				'loginout.php'                     => 'core/loginout',
diff --git a/package-lock.json b/package-lock.json
index c539ceb114a26..ffe9ff267906a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -19527,7 +19527,7 @@
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+			"integrity": "sha1-OBh+wt6nV3//Az/8sSFyaS/24Rg=",
 			"dev": true
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 		"app-root-path": {
@@ -26172,14 +26172,14 @@
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+			"integrity": "sha1-3wEKoSh+Fku9pvlyOwqWoexBh6E=",
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-			"integrity": "sha1-ml9pkFGx5wczKPKgCJaLZOopVdI=",
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 			"dev": true
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@@ -27809,7 +27809,7 @@
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+			"integrity": "sha1-M51M3be2X9YtHfnbn+BN4TQSK9U=",
 			"dev": true
 		},
 		"babel-plugin-apply-mdx-type-prop": {
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+			"integrity": "sha1-dclcMrdI4IUNEMKxaPa9vpiRrOg=",
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+			"integrity": "sha1-MIvur/3ygRkFHvodkyITyRuPkuc=",
 			"dev": true,
 			"optional": true,
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@@ -29206,7 +29206,7 @@
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 					"version": "2.1.1",
 					"resolved": "https://registry.npmjs.org/camelcase/-/camelcase-2.1.1.tgz",
-					"integrity": "sha512-DLIsRzJVBQu72meAKPkWQOLcujdXT32hwdfnkI1frSiSRMK1MofjKHf+MEx0SB6fjEFXL8fBDv1dKymBlOp4Qw==",
+					"integrity": "sha1-fB0W1nmhu+WcoCys7PsBHiAfWh8=",
 					"dev": true,
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-			"integrity": "sha1-4wOogrNCzD7oylE6eZmXNNqzriw=",
+			"integrity": "sha512-QADzlaHc8icV8I7vbaJXJwod9HWYp8uCqf1xa4OfNu1T7JVxQIrUgOWtHdNDtPiywmFbiS12VjotIXLrKM3orQ==",
 			"dev": true
 		},
 		"copy-concurrently": {
@@ -31595,7 +31595,7 @@
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+			"integrity": "sha1-mI3zP+qxke95mmE2nddsF635V+o=",
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+			"integrity": "sha1-uWjGsKBDhDJJAui/Gl3zJXmkUP4=",
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+			"integrity": "sha1-jFoUlNIGbFcMw7/kSWF1rMTVAqs=",
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+			"integrity": "sha1-mqqe7b/7G6OZCnsAEPtnjuAIEgc=",
 			"dev": true,
 			"requires": {
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 					"version": "3.1.0",
 					"resolved": "https://registry.npmjs.org/is-glob/-/is-glob-3.1.0.tgz",
-					"integrity": "sha512-UFpDDrPgM6qpnFNI+rh/p3bUaq9hKLZN8bMUWzxmcnZVS3omf4IPK+BrewlnWjO1WmUsMYuSjKh4UJuV4+Lqmw==",
+					"integrity": "sha1-e6WuJCF4BKxwcHuWkiVnSGzD6Eo=",
 					"dev": true,
 					"requires": {
 						"is-extglob": "^2.1.0"
@@ -38918,7 +38918,7 @@
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 			"version": "0.2.1",
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+			"integrity": "sha1-Sw2hRCEE0bM2NA6AeX6GXPOffXI=",
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@@ -38940,7 +38940,7 @@
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+			"integrity": "sha1-LIlspT25feRdPDMTOmXYyfVjSA0=",
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+			"integrity": "sha1-4mJbrbwNZ8dTPp7cEGjFh65BN+8=",
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@@ -43638,7 +43638,7 @@
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@@ -43652,7 +43652,7 @@
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 					"version": "2.2.0",
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-					"integrity": "sha512-QR/GGaKCkhwk1ePQNYDRKYZ3mwU9ypsKhB0XyFnLQdomyEqk3e8wpW3V5Jp88zbxK4n5ST1nqo+g9juTpownhQ==",
+					"integrity": "sha1-9ID0BDTvgHQfhGkJn43qGPVaTck=",
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@@ -43960,7 +43960,7 @@
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+			"integrity": "sha1-W0b4AUft7leIcPCG0Eghz5mOVR8=",
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@@ -44210,7 +44210,7 @@
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-			"integrity": "sha1-hxDXrwqmJvj/+hzgAWhUUmMlV0g=",
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 		},
@@ -58380,7 +58380,7 @@
 		"untildify": {
 			"version": "2.1.0",
 			"resolved": "https://registry.npmjs.org/untildify/-/untildify-2.1.0.tgz",
-			"integrity": "sha512-sJjbDp2GodvkB0FZZcn7k6afVisqX5BZD7Yq3xp4nN2O15BBK0cLm3Vwn2vQaF7UDS0UUsrQMkkplmDI5fskig==",
+			"integrity": "sha1-F+soB5h/dpUunASF/DEdBqgmouA=",
 			"dev": true,
 			"optional": true,
 			"requires": {
@@ -58656,7 +58656,7 @@
 		"utila": {
 			"version": "0.4.0",
 			"resolved": "https://registry.npmjs.org/utila/-/utila-0.4.0.tgz",
-			"integrity": "sha512-Z0DbgELS9/L/75wZbro8xAnT50pBVFQZ+hUEueGDU5FN51YSCYM+jdxsfCiHjwNP/4LCDD0i/graKpeBnOXKRA==",
+			"integrity": "sha1-ihagXURWV6Oupe7MWxKk+lN5dyw=",
 			"dev": true
 		},
 		"utility-types": {
@@ -58677,7 +58677,7 @@
 		"uuid-browser": {
 			"version": "3.1.0",
 			"resolved": "https://registry.npmjs.org/uuid-browser/-/uuid-browser-3.1.0.tgz",
-			"integrity": "sha512-dsNgbLaTrd6l3MMxTtouOCFw4CBFc/3a+GgYA2YyrJvyQ1u6q4pcu3ktLoUZ/VN/Aw9WsauazbgsgdfVWgAKQg==",
+			"integrity": "sha1-DwWkCu90+eWVHiDvv0SxGHHlZBA=",
 			"dev": true
 		},
 		"v8-compile-cache": {
@@ -60540,7 +60540,7 @@
 		"x-default-browser": {
 			"version": "0.4.0",
 			"resolved": "https://registry.npmjs.org/x-default-browser/-/x-default-browser-0.4.0.tgz",
-			"integrity": "sha512-7LKo7RtWfoFN/rHx1UELv/2zHGMx8MkZKDq1xENmOCTkfIqZJ0zZ26NEJX8czhnPXVcqS0ARjjfJB+eJ0/5Cvw==",
+			"integrity": "sha1-cM8NqF2nwKtcsPFaiX8jIqa91IE=",
 			"dev": true,
 			"requires": {
 				"default-browser-id": "^1.0.4"
diff --git a/packages/block-library/src/group/test/__snapshots__/edit.native.js.snap b/packages/block-library/src/group/test/__snapshots__/edit.native.js.snap
index ee8488edf8864..7234dc54ee4d5 100644
--- a/packages/block-library/src/group/test/__snapshots__/edit.native.js.snap
+++ b/packages/block-library/src/group/test/__snapshots__/edit.native.js.snap
@@ -3,7 +3,7 @@
 exports[`Group block inserts block and adds a Heading block as an inner block 1`] = `
 "<!-- wp:group {\\"layout\\":{\\"type\\":\\"constrained\\"}} -->
 <div class=\\"wp-block-group\\"><!-- wp:heading -->
-<h2></h2>
+<h2 class=\\"wp-block-heading\\"></h2>
 <!-- /wp:heading --></div>
 <!-- /wp:group -->"
 `;
diff --git a/packages/block-library/src/heading/block.json b/packages/block-library/src/heading/block.json
index 89c1514808911..ccafe3bf29613 100644
--- a/packages/block-library/src/heading/block.json
+++ b/packages/block-library/src/heading/block.json
@@ -29,7 +29,7 @@
 	"supports": {
 		"align": [ "wide", "full" ],
 		"anchor": true,
-		"className": false,
+		"className": true,
 		"color": {
 			"gradients": true,
 			"link": true,
diff --git a/packages/block-library/src/heading/index.php b/packages/block-library/src/heading/index.php
new file mode 100644
index 0000000000000..5a7e8dbaab43c
--- /dev/null
+++ b/packages/block-library/src/heading/index.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Appending the wp-block-heading to before rendering the stored `core/heading` block contents.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Adds a wp-block-heading class to the heading block content.
+ *
+ * For example, the following block content:
+ *  <h2 class="align-left">Hello World</h2>
+ *
+ * Would be transformed to:
+ *  <h2 class="align-left wp-block-heading">Hello World</h2>
+ *
+ * @param array  $attributes Attributes of the block being rendered.
+ * @param string $content Content of the block being rendered.
+ *
+ * @return string The content of the block being rendered.
+ */
+function block_core_heading_render( $attributes, $content ) {
+	if ( ! $content ) {
+		return $content;
+	}
+
+	$p = new WP_HTML_Tag_Processor( $content );
+
+	$header_tags = array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' );
+	while ( $p->next_tag() ) {
+		if ( in_array( $p->get_tag(), $header_tags, true ) ) {
+			$p->add_class( 'wp-block-heading' );
+			break;
+		}
+	}
+
+	return $p->get_updated_html();
+}
+
+/**
+ * Registers the `core/heading` block on server.
+ */
+function register_block_core_heading() {
+	register_block_type_from_metadata(
+		__DIR__ . '/heading',
+		array(
+			'render_callback' => 'block_core_heading_render',
+		)
+	);
+}
+
+add_action( 'init', 'register_block_core_heading' );
diff --git a/packages/e2e-tests/specs/editor/blocks/__snapshots__/heading.test.js.snap b/packages/e2e-tests/specs/editor/blocks/__snapshots__/heading.test.js.snap
index b175d82c81d1f..68fd617f7d40c 100644
--- a/packages/e2e-tests/specs/editor/blocks/__snapshots__/heading.test.js.snap
+++ b/packages/e2e-tests/specs/editor/blocks/__snapshots__/heading.test.js.snap
@@ -2,19 +2,19 @@
 
 exports[`Heading can be created by prefixing existing content with number signs and a space 1`] = `
 "<!-- wp:heading {\\"level\\":4} -->
-<h4>4</h4>
+<h4 class=\\"wp-block-heading\\">4</h4>
 <!-- /wp:heading -->"
 `;
 
 exports[`Heading can be created by prefixing number sign and a space 1`] = `
 "<!-- wp:heading {\\"level\\":3} -->
-<h3>3</h3>
+<h3 class=\\"wp-block-heading\\">3</h3>
 <!-- /wp:heading -->"
 `;
 
 exports[`Heading should correctly apply named colors 1`] = `
 "<!-- wp:heading {\\"textColor\\":\\"luminous-vivid-orange\\"} -->
-<h2 class=\\"has-luminous-vivid-orange-color has-text-color\\">Heading</h2>
+<h2 class=\\"wp-block-heading has-luminous-vivid-orange-color has-text-color\\">Heading</h2>
 <!-- /wp:heading -->"
 `;
 
@@ -24,13 +24,13 @@ exports[`Heading should create a paragraph block above when pressing enter at th
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>a</h2>
+<h2 class=\\"wp-block-heading\\">a</h2>
 <!-- /wp:heading -->"
 `;
 
 exports[`Heading should create a paragraph block below when pressing enter at the end 1`] = `
 "<!-- wp:heading -->
-<h2>a</h2>
+<h2 class=\\"wp-block-heading\\">a</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -40,12 +40,12 @@ exports[`Heading should create a paragraph block below when pressing enter at th
 
 exports[`Heading should not work with the list input rule 1`] = `
 "<!-- wp:heading -->
-<h2>1. H</h2>
+<h2 class=\\"wp-block-heading\\">1. H</h2>
 <!-- /wp:heading -->"
 `;
 
 exports[`Heading should work with the format input rules 1`] = `
 "<!-- wp:heading -->
-<h2><code>code</code></h2>
+<h2 class=\\"wp-block-heading\\"><code>code</code></h2>
 <!-- /wp:heading -->"
 `;
diff --git a/packages/e2e-tests/specs/editor/blocks/__snapshots__/quote.test.js.snap b/packages/e2e-tests/specs/editor/blocks/__snapshots__/quote.test.js.snap
index 67f4ef63b49ab..9a3924de6d1da 100644
--- a/packages/e2e-tests/specs/editor/blocks/__snapshots__/quote.test.js.snap
+++ b/packages/e2e-tests/specs/editor/blocks/__snapshots__/quote.test.js.snap
@@ -45,7 +45,7 @@ exports[`Quote can be converted to paragraphs and renders only one paragraph for
 exports[`Quote can be created by converting a heading 1`] = `
 "<!-- wp:quote -->
 <blockquote class=\\"wp-block-quote\\"><!-- wp:heading -->
-<h2>test</h2>
+<h2 class=\\"wp-block-heading\\">test</h2>
 <!-- /wp:heading --></blockquote>
 <!-- /wp:quote -->"
 `;
diff --git a/packages/e2e-tests/specs/editor/blocks/heading.test.js b/packages/e2e-tests/specs/editor/blocks/heading.test.js
index b4181fce6e99d..fb89bed12accc 100644
--- a/packages/e2e-tests/specs/editor/blocks/heading.test.js
+++ b/packages/e2e-tests/specs/editor/blocks/heading.test.js
@@ -87,7 +87,7 @@ describe( 'Heading', () => {
 		await page.keyboard.press( 'Enter' );
 		expect( await getEditedPostContent() ).toMatchInlineSnapshot( `
 		"<!-- wp:heading {\\"level\\":3,\\"style\\":{\\"color\\":{\\"text\\":\\"#4b7f4d\\"}}} -->
-		<h3 class=\\"has-text-color\\" style=\\"color:#4b7f4d\\">Heading</h3>
+		<h3 class=\\"wp-block-heading has-text-color\\" style=\\"color:#4b7f4d\\">Heading</h3>
 		<!-- /wp:heading -->"
 	` );
 	} );
diff --git a/packages/e2e-tests/specs/editor/blocks/quote.test.js b/packages/e2e-tests/specs/editor/blocks/quote.test.js
index bb61fc7a5ee0a..f0d918cf5fa13 100644
--- a/packages/e2e-tests/specs/editor/blocks/quote.test.js
+++ b/packages/e2e-tests/specs/editor/blocks/quote.test.js
@@ -187,13 +187,11 @@ describe( 'Quote', () => {
 		await page.keyboard.press( 'Backspace' );
 
 		expect( await getEditedPostContent() ).toMatchInlineSnapshot( `
-		"<!-- wp:paragraph -->
+		"<!-- wp:quote -->
+		<blockquote class=\\"wp-block-quote\\"><!-- wp:paragraph -->
 		<p>1</p>
-		<!-- /wp:paragraph -->
-
-		<!-- wp:paragraph -->
-		<p>2</p>
-		<!-- /wp:paragraph -->"
+		<!-- /wp:paragraph --><cite>2</cite></blockquote>
+		<!-- /wp:quote -->"
 	` );
 	} );
 } );
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/block-grouping.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/block-grouping.test.js.snap
index 12a32b4e61bd7..39621047016d4 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/block-grouping.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/block-grouping.test.js.snap
@@ -3,7 +3,7 @@
 exports[`Block Grouping Group creation creates a group from multiple blocks of different types via block transforms 1`] = `
 "<!-- wp:group {\\"layout\\":{\\"type\\":\\"constrained\\"}} -->
 <div class=\\"wp-block-group\\"><!-- wp:heading -->
-<h2>Group Heading</h2>
+<h2 class=\\"wp-block-heading\\">Group Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:image -->
@@ -51,7 +51,7 @@ exports[`Block Grouping Group creation creates a group from multiple blocks of t
 exports[`Block Grouping Group creation groups and ungroups multiple blocks of different types via options toolbar 1`] = `
 "<!-- wp:group {\\"layout\\":{\\"type\\":\\"constrained\\"}} -->
 <div class=\\"wp-block-group\\"><!-- wp:heading -->
-<h2>Group Heading</h2>
+<h2 class=\\"wp-block-heading\\">Group Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:image -->
@@ -66,7 +66,7 @@ exports[`Block Grouping Group creation groups and ungroups multiple blocks of di
 
 exports[`Block Grouping Group creation groups and ungroups multiple blocks of different types via options toolbar 2`] = `
 "<!-- wp:heading -->
-<h2>Group Heading</h2>
+<h2 class=\\"wp-block-heading\\">Group Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:image -->
@@ -81,7 +81,7 @@ exports[`Block Grouping Group creation groups and ungroups multiple blocks of di
 exports[`Block Grouping Preserving selected blocks attributes preserves width alignment settings of selected blocks 1`] = `
 "<!-- wp:group {\\"align\\":\\"full\\",\\"layout\\":{\\"type\\":\\"constrained\\"}} -->
 <div class=\\"wp-block-group alignfull\\"><!-- wp:heading -->
-<h2>Group Heading</h2>
+<h2 class=\\"wp-block-heading\\">Group Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:image {\\"align\\":\\"full\\"} -->
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/inserting-blocks.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/inserting-blocks.test.js.snap
index 42789fa855236..b44c552abc789 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/inserting-blocks.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/inserting-blocks.test.js.snap
@@ -71,7 +71,7 @@ exports[`Inserting blocks inserts a block in proper place after having clicked \
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>Heading</h2>
+<h2 class=\\"wp-block-heading\\">Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -93,7 +93,7 @@ exports[`Inserting blocks inserts a block in proper place after having clicked \
 <!-- /wp:cover -->
 
 <!-- wp:heading -->
-<h2>Heading</h2>
+<h2 class=\\"wp-block-heading\\">Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/keep-styles-on-block-transforms.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/keep-styles-on-block-transforms.test.js.snap
index 126fda3cc96e3..be070ef943233 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/keep-styles-on-block-transforms.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/keep-styles-on-block-transforms.test.js.snap
@@ -8,15 +8,15 @@ exports[`Keep styles on block transforms Should keep colors during a transform 1
 
 exports[`Keep styles on block transforms Should keep the font size during a transform from multiple blocks into multiple blocks 1`] = `
 "<!-- wp:heading {\\"fontSize\\":\\"large\\"} -->
-<h2 class=\\"has-large-font-size\\">Line 1 to be made large</h2>
+<h2 class=\\"wp-block-heading has-large-font-size\\">Line 1 to be made large</h2>
 <!-- /wp:heading -->
 
 <!-- wp:heading {\\"fontSize\\":\\"large\\"} -->
-<h2 class=\\"has-large-font-size\\">Line 2 to be made large</h2>
+<h2 class=\\"wp-block-heading has-large-font-size\\">Line 2 to be made large</h2>
 <!-- /wp:heading -->
 
 <!-- wp:heading {\\"fontSize\\":\\"large\\"} -->
-<h2 class=\\"has-large-font-size\\">Line 3 to be made large</h2>
+<h2 class=\\"wp-block-heading has-large-font-size\\">Line 3 to be made large</h2>
 <!-- /wp:heading -->"
 `;
 
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/list-view.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/list-view.test.js.snap
index f0dcd9ca28ff4..eb73b49cd6bd7 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/list-view.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/list-view.test.js.snap
@@ -6,7 +6,7 @@ exports[`List view allows a user to drag a block to a new sibling position 1`] =
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2></h2>
+<h2 class=\\"wp-block-heading\\"></h2>
 <!-- /wp:heading -->
 
 <!-- wp:image -->
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/multi-block-selection.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/multi-block-selection.test.js.snap
index 51e7f452082d8..7dfe4f68d8681 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/multi-block-selection.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/multi-block-selection.test.js.snap
@@ -84,13 +84,13 @@ exports[`Multi-block selection should forward delete across blocks 1`] = `
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>]2</h2>
+<h2 class=\\"wp-block-heading\\">]2</h2>
 <!-- /wp:heading -->"
 `;
 
 exports[`Multi-block selection should forward delete across blocks 2`] = `
 "<!-- wp:heading -->
-<h2>1&amp;2</h2>
+<h2 class=\\"wp-block-heading\\">1&amp;2</h2>
 <!-- /wp:heading -->"
 `;
 
@@ -128,7 +128,7 @@ exports[`Multi-block selection should handle Enter across blocks 1`] = `
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>]2</h2>
+<h2 class=\\"wp-block-heading\\">]2</h2>
 <!-- /wp:heading -->"
 `;
 
@@ -142,7 +142,7 @@ exports[`Multi-block selection should handle Enter across blocks 2`] = `
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>2</h2>
+<h2 class=\\"wp-block-heading\\">2</h2>
 <!-- /wp:heading -->"
 `;
 
diff --git a/packages/e2e-tests/specs/editor/various/__snapshots__/rich-text.test.js.snap b/packages/e2e-tests/specs/editor/various/__snapshots__/rich-text.test.js.snap
index 074158c55f096..025fa91d03c6f 100644
--- a/packages/e2e-tests/specs/editor/various/__snapshots__/rich-text.test.js.snap
+++ b/packages/e2e-tests/specs/editor/various/__snapshots__/rich-text.test.js.snap
@@ -32,7 +32,7 @@ exports[`RichText should handle Home and End keys 1`] = `
 
 exports[`RichText should handle change in tag name gracefully 1`] = `
 "<!-- wp:heading {\\"level\\":3} -->
-<h3></h3>
+<h3 class=\\"wp-block-heading\\"></h3>
 <!-- /wp:heading -->"
 `;
 
diff --git a/packages/react-native-editor/src/initial-html.js b/packages/react-native-editor/src/initial-html.js
index ddea8594b720d..9ef66b83c49c0 100644
--- a/packages/react-native-editor/src/initial-html.js
+++ b/packages/react-native-editor/src/initial-html.js
@@ -1,6 +1,6 @@
 export default `
 <!-- wp:heading -->
-<h2 id="this-is-an-anchor">What is Gutenberg?</h2>
+<h2 class="wp-block-heading" id="this-is-an-anchor">What is Gutenberg?</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -8,7 +8,7 @@ export default `
 <!-- /wp:paragraph -->
 
 <!-- wp:heading {"textAlign":"left","level":4,"className":"has-primary-background-color has-background","style":{"typography":{"lineHeight":"2.5"}}} -->
-<h4 class="has-text-align-left has-primary-background-color has-background" style="line-height:2.5">Heading with line-height set</h4>
+<h4 class="wp-block-heading has-text-align-left has-primary-background-color has-background" style="line-height:2.5">Heading with line-height set</h4>
 <!-- /wp:heading -->
 
 <!-- wp:list -->
diff --git a/phpunit/blocks/render-block-heading-test.php b/phpunit/blocks/render-block-heading-test.php
new file mode 100644
index 0000000000000..59425f25aafd6
--- /dev/null
+++ b/phpunit/blocks/render-block-heading-test.php
@@ -0,0 +1,86 @@
+<?php
+/**
+ * Heading block rendering tests.
+ *
+ * @package WordPress
+ * @subpackage Blocks
+ */
+
+/**
+ * Tests for the Heading block.
+ *
+ * @group blocks
+ */
+class Render_Block_Heading_Test extends WP_UnitTestCase {
+
+
+	/**
+	 * @covers ::gutenberg_block_core_heading_render
+	 * @dataProvider add_css_class_test_examples
+	 */
+	public function test_block_core_heading_render_appends_css_class_to_a_vanilla_element( $input, $expected_result ) {
+		$actual = gutenberg_block_core_heading_render( array(), $input );
+		$this->assertEquals( $expected_result, $actual );
+	}
+
+	public function add_css_class_test_examples() {
+		return array(
+			'should add a class name to a vanilla h2 element' => array(
+				'<h2>Hello World</h2>',
+				'<h2 class="wp-block-heading">Hello World</h2>',
+			),
+			'should not add a class name to a header element' => array(
+				'<header>Hello World</header>',
+				'<header>Hello World</header>',
+			),
+			'should not add a class name to a span element' => array(
+				'<span>Hello World</span>',
+				'<span>Hello World</span>',
+			),
+			'should not add a class name to an invalid h7 element' => array(
+				'<h7>Hello World</h7>',
+				'<h7>Hello World</h7>',
+			),
+			'should add a class name even when the class attribute is already defined' => array(
+				'<h2 class="is-align-right">Hello World</h2>',
+				'<h2 class="is-align-right wp-block-heading">Hello World</h2>',
+			),
+			'should handle single quotes'                => array(
+				"<h2 class='is-align-right'>Hello World</h2>",
+				'<h2 class="is-align-right wp-block-heading">Hello World</h2>',
+			),
+			'should handle single quotes with double quotes inside' => array(
+				"<h2 class='\" is-align-right'>Hello World</h2>",
+				'<h2 class="&quot; is-align-right wp-block-heading">Hello World</h2>',
+			),
+			'should not add a class name even when it is already defined' => array(
+				'<h2 class="is-align-right wp-block-heading">Hello World</h2>',
+				'<h2 class="is-align-right wp-block-heading">Hello World</h2>',
+			),
+			'should add a class name even when there are other HTML attributes present' => array(
+				'<h2 style="display: block">Hello World</h2>',
+				'<h2 class="wp-block-heading" style="display: block">Hello World</h2>',
+			),
+			'should add a class name even when the class attribute is already defined and has many entries' => array(
+				'<h2 class="is-align-right custom   classes">Hello World</h2>',
+				'<h2 class="is-align-right custom   classes wp-block-heading">Hello World</h2>',
+			),
+			'should not add a class name to a nested h2' => array(
+				'<h2 class="is-align-right custom classes"><h2>Hello World</h2></h2>',
+				'<h2 class="is-align-right custom classes wp-block-heading"><h2>Hello World</h2></h2>',
+			),
+			'should not add a class name to a nested h2 when the parent has another attribute' => array(
+				'<h2 style="display: block" class="is-align-right"><h2>Hello World</h2></h2>',
+				'<h2 style="display: block" class="is-align-right wp-block-heading"><h2>Hello World</h2></h2>',
+			),
+			'should add a class name even when the class attribute is surrounded by other attributes' => array(
+				'<h2 style="display: block" class="is-align-right" data-class="corner case!"><h2>Hello World</h2></h2>',
+				'<h2 style="display: block" class="is-align-right wp-block-heading" data-class="corner case!"><h2>Hello World</h2></h2>',
+			),
+			'should add a class name without getting confused when there is a tricky data-class attribute present' => array(
+				'<h2 data-class="corner case!" style="display: block" class="is-align-right"><h2>Hello World</h2></h2>',
+				'<h2 data-class="corner case!" style="display: block" class="is-align-right wp-block-heading"><h2>Hello World</h2></h2>',
+			),
+		);
+	}
+}
diff --git a/test/e2e/specs/editor/blocks/paragraph.spec.js b/test/e2e/specs/editor/blocks/paragraph.spec.js
index 1285955b66734..c713379569b90 100644
--- a/test/e2e/specs/editor/blocks/paragraph.spec.js
+++ b/test/e2e/specs/editor/blocks/paragraph.spec.js
@@ -127,7 +127,7 @@ test.describe( 'Paragraph', () => {
 
 			await expect.poll( editor.getEditedPostContent )
 				.toBe( `<!-- wp:heading -->
-<h2>My Heading</h2>
+<h2 class="wp-block-heading">My Heading</h2>
 <!-- /wp:heading -->` );
 		} );
 
@@ -138,7 +138,9 @@ test.describe( 'Paragraph', () => {
 		} ) => {
 			await editor.insertBlock( { name: 'core/paragraph' } );
 
-			await draggingUtils.simulateDraggingHTML( '<h2>My Heading</h2>' );
+			await draggingUtils.simulateDraggingHTML(
+				'<h2 class="wp-block-heading">My Heading</h2>'
+			);
 
 			const emptyParagraph = page.locator(
 				'[data-type="core/paragraph"][data-empty="true"]'
@@ -153,7 +155,7 @@ test.describe( 'Paragraph', () => {
 
 			await expect.poll( editor.getEditedPostContent )
 				.toBe( `<!-- wp:heading -->
-<h2>My Heading</h2>
+<h2 class="wp-block-heading">My Heading</h2>
 <!-- /wp:heading -->` );
 		} );
 
diff --git a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-1-chromium.txt b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-1-chromium.txt
index aac1718cdb7ff..beef4f8f37b1f 100644
--- a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-1-chromium.txt
+++ b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-1-chromium.txt
@@ -1,5 +1,5 @@
 <!-- wp:heading -->
-<h2>Heading</h2>
+<h2 class="wp-block-heading">Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-2-chromium.txt b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-2-chromium.txt
index ba33f4cbc7c75..4423570da521f 100644
--- a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-2-chromium.txt
+++ b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-cut-partial-selection-and-merge-like-a-normal-delete---not-forward-2-chromium.txt
@@ -1,5 +1,5 @@
 <!-- wp:heading -->
-<h2>ading</h2>
+<h2 class="wp-block-heading">ading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -7,5 +7,5 @@
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>Heph</h2>
+<h2 class="wp-block-heading">Heph</h2>
 <!-- /wp:heading -->
\ No newline at end of file
diff --git a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-1-chromium.txt b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-1-chromium.txt
index aac1718cdb7ff..beef4f8f37b1f 100644
--- a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-1-chromium.txt
+++ b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-1-chromium.txt
@@ -1,5 +1,5 @@
 <!-- wp:heading -->
-<h2>Heading</h2>
+<h2 class="wp-block-heading">Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-2-chromium.txt b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-2-chromium.txt
index e16ec5279cca6..2f13cd0939822 100644
--- a/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-2-chromium.txt
+++ b/test/e2e/specs/editor/various/__snapshots__/Copy-cut-paste-should-paste-plain-text-in-plain-text-context-when-cross-block-selection-is-copied-2-chromium.txt
@@ -1,5 +1,5 @@
 <!-- wp:heading -->
-<h2>Heading</h2>
+<h2 class="wp-block-heading">Heading</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/e2e/specs/editor/various/inserting-blocks.spec.js b/test/e2e/specs/editor/various/inserting-blocks.spec.js
index f45a911650823..fdc4615f197aa 100644
--- a/test/e2e/specs/editor/various/inserting-blocks.spec.js
+++ b/test/e2e/specs/editor/various/inserting-blocks.spec.js
@@ -98,7 +98,7 @@ test.describe( 'Inserting blocks (@firefox, @webkit)', () => {
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2></h2>
+<h2 class="wp-block-heading"></h2>
 <!-- /wp:heading -->` );
 	} );
 
diff --git a/test/e2e/specs/widgets/customizing-widgets.spec.js b/test/e2e/specs/widgets/customizing-widgets.spec.js
index 6b2b06d970e53..776770fecbefe 100644
--- a/test/e2e/specs/widgets/customizing-widgets.spec.js
+++ b/test/e2e/specs/widgets/customizing-widgets.spec.js
@@ -235,7 +235,7 @@ test.describe( 'Widgets Customizer', () => {
 			'sidebar-1'
 		);
 		await requestUtils.addWidgetBlock(
-			`<!-- wp:heading -->\n<h2>First Heading</h2>\n<!-- /wp:heading -->`,
+			`<!-- wp:heading -->\n<h2 class="wp-block-heading">First Heading</h2>\n<!-- /wp:heading -->`,
 			'sidebar-1'
 		);
 
diff --git a/test/integration/__snapshots__/blocks-raw-handling.test.js.snap b/test/integration/__snapshots__/blocks-raw-handling.test.js.snap
index 6c341c815e035..165cdbd79e79a 100644
--- a/test/integration/__snapshots__/blocks-raw-handling.test.js.snap
+++ b/test/integration/__snapshots__/blocks-raw-handling.test.js.snap
@@ -20,7 +20,7 @@ exports[`Blocks raw handling pasteHandler should strip some text-level elements
 
 exports[`Blocks raw handling pasteHandler should strip windows data 1`] = `
 "<!-- wp:heading -->
-<h2>Heading Win</h2>
+<h2 class=\\"wp-block-heading\\">Heading Win</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -31,7 +31,7 @@ exports[`Blocks raw handling pasteHandler should strip windows data 1`] = `
 exports[`Blocks raw handling should correctly handle quotes with mixed content 1`] = `
 "<!-- wp:quote -->
 <blockquote class=\\"wp-block-quote\\"><!-- wp:heading {\\"level\\":1} -->
-<h1>chicken</h1>
+<h1 class=\\"wp-block-heading\\">chicken</h1>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -42,7 +42,7 @@ exports[`Blocks raw handling should correctly handle quotes with mixed content 1
 
 exports[`rawHandler should convert HTML post to blocks with minimal content changes 1`] = `
 "<!-- wp:heading -->
-<h2>Howdy</h2>
+<h2 class=\\"wp-block-heading\\">Howdy</h2>
 <!-- /wp:heading -->
 
 <!-- wp:image -->
@@ -58,7 +58,7 @@ exports[`rawHandler should convert HTML post to blocks with minimal content chan
 <!-- /wp:paragraph -->
 
 <!-- wp:heading {\\"level\\":3} -->
-<h3>More tag</h3>
+<h3 class=\\"wp-block-heading\\">More tag</h3>
 <!-- /wp:heading -->
 
 <!-- wp:more -->
@@ -66,7 +66,7 @@ exports[`rawHandler should convert HTML post to blocks with minimal content chan
 <!-- /wp:more -->
 
 <!-- wp:heading {\\"level\\":3} -->
-<h3>Shortcode</h3>
+<h3 class=\\"wp-block-heading\\">Shortcode</h3>
 <!-- /wp:heading -->
 
 <!-- wp:gallery {\\"columns\\":3,\\"linkTo\\":\\"none\\"} -->
@@ -98,7 +98,7 @@ exports[`rawHandler should convert HTML post to blocks with minimal content chan
 
 <!-- wp:quote -->
 <blockquote class=\\"wp-block-quote\\"><!-- wp:heading {\\"level\\":1} -->
-<h1>Heading</h1>
+<h1 class=\\"wp-block-heading\\">Heading</h1>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/blocks-raw-handling.test.js b/test/integration/blocks-raw-handling.test.js
index 2bc08c9a7b35a..f7d7320114072 100644
--- a/test/integration/blocks-raw-handling.test.js
+++ b/test/integration/blocks-raw-handling.test.js
@@ -249,7 +249,7 @@ describe( 'Blocks raw handling', () => {
 			.join( '' );
 
 		expect( filtered ).toBe(
-			'<h1>Some <em>heading</em></h1><p>A paragraph.</p>'
+			'<h1 class="wp-block-heading">Some <em>heading</em></h1><p>A paragraph.</p>'
 		);
 		expect( console ).toHaveLogged();
 	} );
@@ -336,7 +336,7 @@ describe( 'Blocks raw handling', () => {
 	it( 'should correctly handle quotes with mixed content', () => {
 		const filtered = serialize(
 			pasteHandler( {
-				HTML: '<blockquote><h1>chicken</h1><p>ribs</p></blockquote>',
+				HTML: '<blockquote><h1 class="wp-block-heading">chicken</h1><p>ribs</p></blockquote>',
 				mode: 'AUTO',
 			} )
 		);
diff --git a/test/integration/fixtures/blocks/core__heading__deprecated-1.serialized.html b/test/integration/fixtures/blocks/core__heading__deprecated-1.serialized.html
index 0a2f890302c3f..a064b6f60cf04 100644
--- a/test/integration/fixtures/blocks/core__heading__deprecated-1.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__deprecated-1.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textAlign":"right","level":3} -->
-<h3 class="has-text-align-right">A picture is worth a thousand words, or so the saying goes</h3>
+<h3 class="wp-block-heading has-text-align-right">A picture is worth a thousand words, or so the saying goes</h3>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__deprecated-2.serialized.html b/test/integration/fixtures/blocks/core__heading__deprecated-2.serialized.html
index 1dbaea2593eb9..989d82a8d7fca 100644
--- a/test/integration/fixtures/blocks/core__heading__deprecated-2.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__deprecated-2.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textColor":"accent"} -->
-<h2 class="has-accent-color has-text-color">text</h2>
+<h2 class="wp-block-heading has-accent-color has-text-color">text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__deprecated-3.serialized.html b/test/integration/fixtures/blocks/core__heading__deprecated-3.serialized.html
index c2c4470e500f1..2e04a7e01f977 100644
--- a/test/integration/fixtures/blocks/core__heading__deprecated-3.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__deprecated-3.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"style":{"color":{"text":"#268ebb"}}} -->
-<h2 class="has-text-color" style="color:#268ebb">Text</h2>
+<h2 class="wp-block-heading has-text-color" style="color:#268ebb">Text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__deprecated-4.serialized.html b/test/integration/fixtures/blocks/core__heading__deprecated-4.serialized.html
index 2e4f98cda15ff..cc4218e776a73 100644
--- a/test/integration/fixtures/blocks/core__heading__deprecated-4.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__deprecated-4.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textAlign":"center","textColor":"accent"} -->
-<h2 class="has-text-align-center has-accent-color has-text-color">Text</h2>
+<h2 class="wp-block-heading has-text-align-center has-accent-color has-text-color">Text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__h2-color.html b/test/integration/fixtures/blocks/core__heading__h2-color.html
index 23c39f701c765..7d1dee6d70632 100644
--- a/test/integration/fixtures/blocks/core__heading__h2-color.html
+++ b/test/integration/fixtures/blocks/core__heading__h2-color.html
@@ -1,4 +1,4 @@
 <!-- wp:heading {"textColor":"accent"} -->
-<h2 class="has-accent-color has-text-color">Text</h2>
+<h2 class="wp-block-heading has-accent-color has-text-color">Text</h2>
 <!-- /wp:heading -->
 
diff --git a/test/integration/fixtures/blocks/core__heading__h2-color.parsed.json b/test/integration/fixtures/blocks/core__heading__h2-color.parsed.json
index 64a2fb552e7fb..763648f6d6112 100644
--- a/test/integration/fixtures/blocks/core__heading__h2-color.parsed.json
+++ b/test/integration/fixtures/blocks/core__heading__h2-color.parsed.json
@@ -5,9 +5,9 @@
 			"textColor": "accent"
 		},
 		"innerBlocks": [],
-		"innerHTML": "\n<h2 class=\"has-accent-color has-text-color\">Text</h2>\n",
+		"innerHTML": "\n<h2 class=\"wp-block-heading has-accent-color has-text-color\">Text</h2>\n",
 		"innerContent": [
-			"\n<h2 class=\"has-accent-color has-text-color\">Text</h2>\n"
+			"\n<h2 class=\"wp-block-heading has-accent-color has-text-color\">Text</h2>\n"
 		]
 	}
 ]
diff --git a/test/integration/fixtures/blocks/core__heading__h2-color.serialized.html b/test/integration/fixtures/blocks/core__heading__h2-color.serialized.html
index 862a62b2d7975..73bb943850272 100644
--- a/test/integration/fixtures/blocks/core__heading__h2-color.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__h2-color.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textColor":"accent"} -->
-<h2 class="has-accent-color has-text-color">Text</h2>
+<h2 class="wp-block-heading has-accent-color has-text-color">Text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__h2.html b/test/integration/fixtures/blocks/core__heading__h2.html
index a55b391a25057..d7b487af0b670 100644
--- a/test/integration/fixtures/blocks/core__heading__h2.html
+++ b/test/integration/fixtures/blocks/core__heading__h2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2>A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__h2.parsed.json b/test/integration/fixtures/blocks/core__heading__h2.parsed.json
index 7e8932f95e5de..ab763edaea5ec 100644
--- a/test/integration/fixtures/blocks/core__heading__h2.parsed.json
+++ b/test/integration/fixtures/blocks/core__heading__h2.parsed.json
@@ -3,9 +3,9 @@
 		"blockName": "core/heading",
 		"attrs": {},
 		"innerBlocks": [],
-		"innerHTML": "\n<h2>A picture is worth a thousand words, or so the saying goes</h2>\n",
+		"innerHTML": "\n<h2 class=\"wp-block-heading\">A picture is worth a thousand words, or so the saying goes</h2>\n",
 		"innerContent": [
-			"\n<h2>A picture is worth a thousand words, or so the saying goes</h2>\n"
+			"\n<h2 class=\"wp-block-heading\">A picture is worth a thousand words, or so the saying goes</h2>\n"
 		]
 	}
 ]
diff --git a/test/integration/fixtures/blocks/core__heading__h2.serialized.html b/test/integration/fixtures/blocks/core__heading__h2.serialized.html
index 1212bf83c3029..96cc3063da105 100644
--- a/test/integration/fixtures/blocks/core__heading__h2.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__h2.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading -->
-<h2>A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__h4-em.html b/test/integration/fixtures/blocks/core__heading__h4-em.html
index bd13c30bb968d..0a72af58e24db 100644
--- a/test/integration/fixtures/blocks/core__heading__h4-em.html
+++ b/test/integration/fixtures/blocks/core__heading__h4-em.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading {"level":4} -->
-<h4>The <em>Inserter</em> Tool</h4>
+<h4 class="wp-block-heading">The <em>Inserter</em> Tool</h4>
 <!-- /wp:core/heading -->
diff --git a/test/integration/fixtures/blocks/core__heading__h4-em.parsed.json b/test/integration/fixtures/blocks/core__heading__h4-em.parsed.json
index 283fd532b3fd2..b8cd44ca0471e 100644
--- a/test/integration/fixtures/blocks/core__heading__h4-em.parsed.json
+++ b/test/integration/fixtures/blocks/core__heading__h4-em.parsed.json
@@ -5,7 +5,9 @@
 			"level": 4
 		},
 		"innerBlocks": [],
-		"innerHTML": "\n<h4>The <em>Inserter</em> Tool</h4>\n",
-		"innerContent": [ "\n<h4>The <em>Inserter</em> Tool</h4>\n" ]
+		"innerHTML": "\n<h4 class=\"wp-block-heading\">The <em>Inserter</em> Tool</h4>\n",
+		"innerContent": [
+			"\n<h4 class=\"wp-block-heading\">The <em>Inserter</em> Tool</h4>\n"
+		]
 	}
 ]
diff --git a/test/integration/fixtures/blocks/core__heading__h4-em.serialized.html b/test/integration/fixtures/blocks/core__heading__h4-em.serialized.html
index 051e1c9f39b27..d7a3b904dbd9a 100644
--- a/test/integration/fixtures/blocks/core__heading__h4-em.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading__h4-em.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"level":4} -->
-<h4>The <em>Inserter</em> Tool</h4>
+<h4 class="wp-block-heading">The <em>Inserter</em> Tool</h4>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading_align-textalign.html b/test/integration/fixtures/blocks/core__heading_align-textalign.html
index 26c8041d1b97a..3f7fb12335b4b 100644
--- a/test/integration/fixtures/blocks/core__heading_align-textalign.html
+++ b/test/integration/fixtures/blocks/core__heading_align-textalign.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textAlign":"center","align":"wide"} -->
-<h2 class="alignwide has-text-align-center">Text</h2>
+<h2 class="wp-block-heading alignwide has-text-align-center">Text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/blocks/core__heading_align-textalign.parsed.json b/test/integration/fixtures/blocks/core__heading_align-textalign.parsed.json
index 918ba0e5c79bb..bd378de8f71dc 100644
--- a/test/integration/fixtures/blocks/core__heading_align-textalign.parsed.json
+++ b/test/integration/fixtures/blocks/core__heading_align-textalign.parsed.json
@@ -6,9 +6,9 @@
 			"align": "wide"
 		},
 		"innerBlocks": [],
-		"innerHTML": "\n<h2 class=\"alignwide has-text-align-center\">Text</h2>\n",
+		"innerHTML": "\n<h2 class=\"wp-block-heading alignwide has-text-align-center\">Text</h2>\n",
 		"innerContent": [
-			"\n<h2 class=\"alignwide has-text-align-center\">Text</h2>\n"
+			"\n<h2 class=\"wp-block-heading alignwide has-text-align-center\">Text</h2>\n"
 		]
 	}
 ]
diff --git a/test/integration/fixtures/blocks/core__heading_align-textalign.serialized.html b/test/integration/fixtures/blocks/core__heading_align-textalign.serialized.html
index 26c8041d1b97a..3f7fb12335b4b 100644
--- a/test/integration/fixtures/blocks/core__heading_align-textalign.serialized.html
+++ b/test/integration/fixtures/blocks/core__heading_align-textalign.serialized.html
@@ -1,3 +1,3 @@
 <!-- wp:heading {"textAlign":"center","align":"wide"} -->
-<h2 class="alignwide has-text-align-center">Text</h2>
+<h2 class="wp-block-heading alignwide has-text-align-center">Text</h2>
 <!-- /wp:heading -->
diff --git a/test/integration/fixtures/documents/google-docs-out.html b/test/integration/fixtures/documents/google-docs-out.html
index db8bc81948fcc..e88311fab7b1f 100644
--- a/test/integration/fixtures/documents/google-docs-out.html
+++ b/test/integration/fixtures/documents/google-docs-out.html
@@ -3,7 +3,7 @@
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>This is a <em>heading</em></h2>
+<h2 class="wp-block-heading">This is a <em>heading</em></h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/fixtures/documents/google-docs-with-comments-out.html b/test/integration/fixtures/documents/google-docs-with-comments-out.html
index db8bc81948fcc..e88311fab7b1f 100644
--- a/test/integration/fixtures/documents/google-docs-with-comments-out.html
+++ b/test/integration/fixtures/documents/google-docs-with-comments-out.html
@@ -3,7 +3,7 @@
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>This is a <em>heading</em></h2>
+<h2 class="wp-block-heading">This is a <em>heading</em></h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/fixtures/documents/markdown-out.html b/test/integration/fixtures/documents/markdown-out.html
index c1237925a750b..31fa8dacbebf0 100644
--- a/test/integration/fixtures/documents/markdown-out.html
+++ b/test/integration/fixtures/documents/markdown-out.html
@@ -1,5 +1,5 @@
 <!-- wp:heading {"level":1} -->
-<h1>This is a heading with <em>italic</em></h1>
+<h1 class="wp-block-heading">This is a heading with <em>italic</em></h1>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -11,7 +11,7 @@ <h1>This is a heading with <em>italic</em></h1>
 <!-- /wp:paragraph -->
 
 <!-- wp:heading -->
-<h2>Lists</h2>
+<h2 class="wp-block-heading">Lists</h2>
 <!-- /wp:heading -->
 
 <!-- wp:list -->
@@ -47,7 +47,7 @@ <h2>Lists</h2>
 <!-- /wp:list -->
 
 <!-- wp:heading -->
-<h2>Table</h2>
+<h2 class="wp-block-heading">Table</h2>
 <!-- /wp:heading -->
 
 <!-- wp:table -->
@@ -59,7 +59,7 @@ <h2>Table</h2>
 <!-- /wp:table -->
 
 <!-- wp:heading -->
-<h2>Quote</h2>
+<h2 class="wp-block-heading">Quote</h2>
 <!-- /wp:heading -->
 
 <!-- wp:quote -->
@@ -73,7 +73,7 @@ <h2>Quote</h2>
 <!-- /wp:quote -->
 
 <!-- wp:heading -->
-<h2>Code</h2>
+<h2 class="wp-block-heading">Code</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/fixtures/documents/ms-word-out.html b/test/integration/fixtures/documents/ms-word-out.html
index 9a5d5fdf557a4..0b1a3e00fe84d 100644
--- a/test/integration/fixtures/documents/ms-word-out.html
+++ b/test/integration/fixtures/documents/ms-word-out.html
@@ -7,11 +7,11 @@
 <!-- /wp:paragraph -->
 
 <!-- wp:heading {"level":1} -->
-<h1>This is a heading level 1</h1>
+<h1 class="wp-block-heading">This is a heading level 1</h1>
 <!-- /wp:heading -->
 
 <!-- wp:heading -->
-<h2>This is a heading level 2</h2>
+<h2 class="wp-block-heading">This is a heading level 2</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/fixtures/documents/windows.html b/test/integration/fixtures/documents/windows.html
index 022cc8f53b0fa..1d6125160ec08 100644
--- a/test/integration/fixtures/documents/windows.html
+++ b/test/integration/fixtures/documents/windows.html
@@ -1,6 +1,6 @@
 <html><body>
 <!--StartFragment--><!-- wp:heading -->
-<h2>Heading Win</h2>
+<h2 class="wp-block-heading">Heading Win</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
diff --git a/test/integration/fixtures/documents/wordpress-out.html b/test/integration/fixtures/documents/wordpress-out.html
index 03ab224fa1028..c394fa232081d 100644
--- a/test/integration/fixtures/documents/wordpress-out.html
+++ b/test/integration/fixtures/documents/wordpress-out.html
@@ -1,5 +1,5 @@
 <!-- wp:heading -->
-<h2>Howdy</h2>
+<h2 class="wp-block-heading">Howdy</h2>
 <!-- /wp:heading -->
 
 <!-- wp:paragraph -->
@@ -7,7 +7,7 @@ <h2>Howdy</h2>
 <!-- /wp:paragraph -->
 
 <!-- wp:heading {"level":3} -->
-<h3>More tag</h3>
+<h3 class="wp-block-heading">More tag</h3>
 <!-- /wp:heading -->
 
 <!-- wp:more -->
@@ -15,7 +15,7 @@ <h3>More tag</h3>
 <!-- /wp:more -->
 
 <!-- wp:heading {"level":3} -->
-<h3>Shortcode</h3>
+<h3 class="wp-block-heading">Shortcode</h3>
 <!-- /wp:heading -->
 
 <!-- wp:gallery {"columns":3,"linkTo":"none"} -->