diff --git a/amp.php b/amp.php
index f854b6caea3..3bbb9ac540f 100644
--- a/amp.php
+++ b/amp.php
@@ -127,7 +127,20 @@ function amp_force_query_var_value( $query_vars ) {
  * @return void
  */
 function amp_maybe_add_actions() {
-	if ( amp_is_canonical() || ! is_singular() || is_feed() ) {
+
+	// Add hooks for when a themes that support AMP.
+	if ( current_theme_supports( 'amp' ) ) {
+		if ( amp_is_canonical() ) {
+			AMP_Canonical_Mode_Actions::register_hooks();
+		} elseif ( is_amp_endpoint() ) {
+			AMP_Paired_Mode_Actions::register_hooks();
+		} else {
+			AMP_Frontend_Actions::register_hooks();
+		}
+		return;
+	}
+
+	if ( ! is_singular() || is_feed() ) {
 		return;
 	}
 
diff --git a/includes/actions/class-amp-canonical-mode-actions.php b/includes/actions/class-amp-canonical-mode-actions.php
new file mode 100644
index 00000000000..952da21096e
--- /dev/null
+++ b/includes/actions/class-amp-canonical-mode-actions.php
@@ -0,0 +1,191 @@
+<?php
+/**
+ * Class AMP_Canonical_Mode_Actions
+ *
+ * @package AMP
+ */
+
+/**
+ * Class AMP_Canonical_Mode_Actions
+ *
+ * Callbacks for adding AMP-related things to the theme when in canonical mode.
+ */
+class AMP_Canonical_Mode_Actions {
+
+	/**
+	 * Register hooks.
+	 */
+	public static function register_hooks() {
+
+		// Remove core actions which are invalid AMP.
+		remove_action( 'wp_head', 'locale_stylesheet' );
+		remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
+		remove_action( 'wp_head', 'wp_print_styles', 8 );
+		remove_action( 'wp_head', 'wp_print_head_scripts', 9 );
+		remove_action( 'wp_head', 'wp_custom_css_cb', 101 );
+		remove_action( 'wp_footer', 'wp_print_footer_scripts', 20 );
+		remove_action( 'wp_print_styles', 'print_emoji_styles' );
+
+		// Replace core's canonical link functionality with one that outputs links for non-singular queries as well. See WP Core #18660.
+		remove_action( 'wp_head', 'rel_canonical' );
+		add_action( 'wp_head', array( __CLASS__, 'rel_canonical' ), 1 );
+
+		// Add additional markup required by AMP <https://www.ampproject.org/docs/reference/spec#required-markup>.
+		add_action( 'wp_head', array( __CLASS__, 'print_meta_charset' ), 0 );
+		add_action( 'wp_head', array( __CLASS__, 'print_meta_viewport' ), 2 );
+		add_action( 'wp_head', array( __CLASS__, 'print_amp_boilerplate_code' ), 3 );
+		add_action( 'wp_head', array( __CLASS__, 'print_amp_scripts' ), 4 );
+		add_action( 'wp_head', array( __CLASS__, 'print_amp_custom_style' ), 5 );
+
+		add_action( 'admin_bar_init', array( __CLASS__, 'admin_bar_init' ) );
+		add_theme_support( 'admin-bar', array( 'callback' => '__return_false' ) );
+
+		// @todo Add output buffering.
+		// @todo Add character conversion.
+	}
+
+	/**
+	 * Print meta charset tag.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#chrs
+	 */
+	public static function print_meta_charset() {
+		echo '<meta charset="utf-8">';
+	}
+
+	/**
+	 * Print meta charset tag.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#vprt
+	 */
+	public static function print_meta_viewport() {
+		echo '<meta name="viewport" content="width=device-width,minimum-scale=1">';
+	}
+
+	/**
+	 * Print AMP boilerplate code.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#boilerplate
+	 */
+	public static function print_amp_boilerplate_code() {
+		echo '<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style>';
+		echo '<noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>';
+	}
+
+	/**
+	 * Print AMP script and placeholder for others.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#scrpt
+	 */
+	public static function print_amp_scripts() {
+		echo '<script async src="https://cdn.ampproject.org/v0.js"></script>'; // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		echo '<!--AMP_PLUGIN_SCRIPTS_PLACEHOLDER-->'; // Replaced after output buffering with all AMP component scripts.
+	}
+
+	/**
+	 * Add canonical link.
+	 *
+	 * Replaces `rel_canonical()` which only outputs canonical URLs for singular posts and pages.
+	 * This can be removed once WP Core #18660 lands.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#canon.
+	 * @link https://core.trac.wordpress.org/ticket/18660
+	 *
+	 * @see rel_canonical()
+	 * @global WP $wp
+	 * @global WP_Rewrite $wp_rewrite
+	 */
+	public static function rel_canonical() {
+		global $wp, $wp_rewrite;
+
+		$url = null;
+		if ( is_singular() ) {
+			$url = wp_get_canonical_url();
+		}
+
+		// For non-singular queries, make use of the request URI and public query vars to determine canonical URL.
+		if ( empty( $url ) ) {
+			$added_query_vars = $wp->query_vars;
+			if ( ! $wp_rewrite->permalink_structure || empty( $wp->request ) ) {
+				$url = home_url( '/' );
+			} else {
+				$url = home_url( user_trailingslashit( $wp->request ) );
+				parse_str( $wp->matched_query, $matched_query_vars );
+				foreach ( $wp->query_vars as $key => $value ) {
+
+					// Remove query vars that were matched in the rewrite rules for the request.
+					if ( isset( $matched_query_vars[ $key ] ) ) {
+						unset( $added_query_vars[ $key ] );
+					}
+				}
+			}
+		}
+
+		if ( ! empty( $added_query_vars ) ) {
+			$url = add_query_arg( $added_query_vars, $url );
+		}
+
+		echo '<link rel="canonical" href="' . esc_url( $url ) . '">' . "\n";
+	}
+
+	/**
+	 * Print Custom AMP styles.
+	 *
+	 * @see wp_custom_css_cb()
+	 */
+	public static function print_amp_custom_style() {
+		echo '<style amp-custom>';
+
+		// @todo Grab source of all enqueued styles and concatenate here?
+		// @todo Print contents of get_locale_stylesheet_uri()?
+		// @todo Allow this to be filtered after output buffering is complete so additional styles can be added by widgets and other components just-in-time?
+		$path = get_template_directory() . '/style.css'; // @todo Honor filter in get_stylesheet_directory_uri()? Style must be local.
+		$css  = file_get_contents( $path ); // phpcs:ignore WordPress.WP.AlternativeFunctions -- It's not a remote file.
+		echo wp_strip_all_tags( $css ); // WPCS: XSS OK.
+
+		// Implement AMP version of wp_custom_css_cb().
+		$custom_css = trim( wp_get_custom_css() );
+		if ( ! empty( $custom_css ) ) {
+			echo '/* start:wp_get_custom_css */';
+			echo wp_strip_all_tags( wp_get_custom_css() ); // WPCS: XSS OK.
+			echo '/* end:wp_get_custom_css */';
+		}
+		echo '</style>';
+	}
+
+	/**
+	 * Fix up admin bar.
+	 */
+	public static function admin_bar_init() {
+		remove_action( 'wp_head', 'wp_admin_bar_header' );
+		add_action( 'admin_bar_menu', array( __CLASS__, 'remove_customize_support_script' ), 100 ); // See WP_Admin_Bar::add_menus().
+		add_filter( 'body_class', array( __CLASS__, array( __CLASS__, 'filter_body_class_to_force_customize_support' ) ) );
+	}
+
+	/**
+	 * Let the body class include customize-support by default since support script won't be able to dynamically add it.
+	 *
+	 * @see wp_customize_support_script()
+	 *
+	 * @param array $classes Body classes.
+	 * @return array Classes.
+	 */
+	public static function filter_body_class_to_force_customize_support( $classes ) {
+		$i = array_search( 'no-customize-support', $classes, true );
+		if ( false !== $i ) {
+			array_splice( $classes, $i, 1 );
+		}
+		$classes[] = 'customize-support';
+		return $classes;
+	}
+
+	/**
+	 * Remove Customizer support script.
+	 *
+	 * @see WP_Admin_Bar::add_menus()
+	 * @see wp_customize_support_script()
+	 */
+	public static function remove_customize_support_script() {
+		remove_action( 'wp_before_admin_bar_render', 'wp_customize_support_script' );
+	}
+}
diff --git a/includes/actions/class-amp-paired-mode-actions.php b/includes/actions/class-amp-paired-mode-actions.php
new file mode 100644
index 00000000000..8e3531936b1
--- /dev/null
+++ b/includes/actions/class-amp-paired-mode-actions.php
@@ -0,0 +1,21 @@
+<?php
+/**
+ * Class AMP_Paired_Mode_Actions
+ *
+ * @package AMP
+ */
+
+/**
+ * Class AMP_Paired_Mode_Actions
+ *
+ * Callbacks for adding AMP-related things to the theme when in paired mode, for themes that support amp.
+ */
+class AMP_Paired_Mode_Actions {
+
+	/**
+	 * Register hooks.
+	 */
+	public static function register_hooks() {
+		// @todo See https://github.com/Automattic/amp-wp/issues/849.
+	}
+}
diff --git a/includes/class-amp-autoloader.php b/includes/class-amp-autoloader.php
index 082988c34a4..001cb1b0405 100644
--- a/includes/class-amp-autoloader.php
+++ b/includes/class-amp-autoloader.php
@@ -32,6 +32,8 @@ class AMP_Autoloader {
 		'AMP_Actions'                                 => 'includes/actions/class-amp-actions',
 		'AMP_Frontend_Actions'                        => 'includes/actions/class-amp-frontend-actions',
 		'AMP_Paired_Post_Actions'                     => 'includes/actions/class-amp-paired-post-actions',
+		'AMP_Paired_Mode_Actions'                     => 'includes/actions/class-amp-paired-mode-actions',
+		'AMP_Canonical_Mode_Actions'                  => 'includes/actions/class-amp-canonical-mode-actions',
 		'AMP_Template_Customizer'                     => 'includes/admin/class-amp-customizer',
 		'AMP_Post_Meta_Box'                           => 'includes/admin/class-amp-post-meta-box',
 		'AMP_Post_Type_Support'                       => 'includes/class-amp-post-type-support',