Index: src/wp-includes/general-template.php
===================================================================
--- src/wp-includes/general-template.php	(revision 40856)
+++ src/wp-includes/general-template.php	(working copy)
@@ -43,6 +43,18 @@
 	$templates[] = 'header.php';
 
 	locate_template( $templates, true );
+
+	/**
+	 * Fires after the header template file is loaded.
+	 *
+	 * The hook allows markup or additional template files to be loaded after the
+	 * results of a get_header() call.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param string|null $name Name of the specific header file to use. null for the default header.
+	 */
+	do_action( 'after_get_header', $name );
 }
 
 /**
@@ -82,6 +94,18 @@
 	$templates[]    = 'footer.php';
 
 	locate_template( $templates, true );
+
+	/**
+	 * Fires after the footer template file is loaded.
+	 *
+	 * The hook allows markup or additional template files to be loaded after the
+	 * results of a get_footer() call.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param string|null $name Name of the specific footer file to use. null for the default footer.
+	 */
+	do_action( 'after_get_footer', $name );
 }
 
 /**