diff --git src/wp-content/themes/twentyeleven/header.php src/wp-content/themes/twentyeleven/header.php
index f9be4f52e0..2b7f5b35eb 100644
--- src/wp-content/themes/twentyeleven/header.php
+++ src/wp-content/themes/twentyeleven/header.php
@@ -68,6 +68,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="hfeed">
 	<header id="branding" role="banner">
 			<hgroup>
diff --git src/wp-content/themes/twentyfifteen/header.php src/wp-content/themes/twentyfifteen/header.php
index 28de34ed9f..1698d6b734 100644
--- src/wp-content/themes/twentyfifteen/header.php
+++ src/wp-content/themes/twentyfifteen/header.php
@@ -22,6 +22,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="hfeed site">
 	<a class="skip-link screen-reader-text" href="#content"><?php _e( 'Skip to content', 'twentyfifteen' ); ?></a>
 
diff --git src/wp-content/themes/twentyfourteen/header.php src/wp-content/themes/twentyfourteen/header.php
index 7286d88938..d1318d628a 100644
--- src/wp-content/themes/twentyfourteen/header.php
+++ src/wp-content/themes/twentyfourteen/header.php
@@ -31,6 +31,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="hfeed site">
 	<?php if ( get_header_image() ) : ?>
 	<div id="site-header">
diff --git src/wp-content/themes/twentyseventeen/header.php src/wp-content/themes/twentyseventeen/header.php
index 27148be6d4..0ac11c30ec 100644
--- src/wp-content/themes/twentyseventeen/header.php
+++ src/wp-content/themes/twentyseventeen/header.php
@@ -23,6 +23,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="site">
 	<a class="skip-link screen-reader-text" href="#content"><?php _e( 'Skip to content', 'twentyseventeen' ); ?></a>
 
diff --git src/wp-content/themes/twentysixteen/header.php src/wp-content/themes/twentysixteen/header.php
index d230c4f8db..083e18c9e0 100644
--- src/wp-content/themes/twentysixteen/header.php
+++ src/wp-content/themes/twentysixteen/header.php
@@ -22,6 +22,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="site">
 	<div class="site-inner">
 		<a class="skip-link screen-reader-text" href="#content"><?php _e( 'Skip to content', 'twentysixteen' ); ?></a>
diff --git src/wp-content/themes/twentyten/header.php src/wp-content/themes/twentyten/header.php
index 1ff063b8f0..94a9f1e916 100644
--- src/wp-content/themes/twentyten/header.php
+++ src/wp-content/themes/twentyten/header.php
@@ -55,6 +55,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="wrapper" class="hfeed">
 	<div id="header">
 		<div id="masthead">
diff --git src/wp-content/themes/twentythirteen/header.php src/wp-content/themes/twentythirteen/header.php
index 094f74cc9f..3af541e013 100644
--- src/wp-content/themes/twentythirteen/header.php
+++ src/wp-content/themes/twentythirteen/header.php
@@ -31,6 +31,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+	<?php wp_body_open(); ?>
 	<div id="page" class="hfeed site">
 		<header id="masthead" class="site-header" role="banner">
 			<a class="home-link" href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
diff --git src/wp-content/themes/twentytwelve/header.php src/wp-content/themes/twentytwelve/header.php
index c3b99d6f3d..c8dc7eea51 100644
--- src/wp-content/themes/twentytwelve/header.php
+++ src/wp-content/themes/twentytwelve/header.php
@@ -32,6 +32,7 @@
 </head>
 
 <body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
 <div id="page" class="hfeed site">
 	<header id="masthead" class="site-header" role="banner">
 		<hgroup>
@@ -50,4 +51,4 @@
 		<?php endif; ?>
 	</header><!-- #masthead -->
 
-	<div id="main" class="wrapper">
\ No newline at end of file
+	<div id="main" class="wrapper">
diff --git src/wp-includes/general-template.php src/wp-includes/general-template.php
index 915aea540e..22d133b3f6 100644
--- src/wp-includes/general-template.php
+++ src/wp-includes/general-template.php
@@ -2631,6 +2631,22 @@ function wp_footer() {
 }
 
 /**
+ * Fire the wp_body_open action
+ *
+ * * See {@see 'wp_body_open'}.
+ *
+ * @since 5.0
+ */
+function wp_body_open() {
+	/**
+	 * Allows access to templates after the opening <body> tag.
+	 *
+	 * @since 5.0
+	 */
+	do_action( 'wp_body_open' );
+}
+
+/**
  * Display the links to the general feeds.
  *
  * @since 2.8.0
