Index: src/wp-admin/network/themes.php
===================================================================
--- src/wp-admin/network/themes.php	(revision 37177)
+++ src/wp-admin/network/themes.php	(working copy)
@@ -29,12 +29,10 @@
 $referer = remove_query_arg( $temp_args, wp_get_referer() );
 
 if ( $action ) {
-	$allowed_themes = get_site_option( 'allowedthemes' );
 	switch ( $action ) {
 		case 'enable':
 			check_admin_referer('enable-theme_' . $_GET['theme']);
-			$allowed_themes[ $_GET['theme'] ] = true;
-			update_site_option( 'allowedthemes', $allowed_themes );
+			WP_Theme::network_enable_theme( $_GET['theme'] );
 			if ( false === strpos( $referer, '/network/themes.php' ) )
 				wp_redirect( network_admin_url( 'themes.php?enabled=1' ) );
 			else
@@ -42,8 +40,7 @@
 			exit;
 		case 'disable':
 			check_admin_referer('disable-theme_' . $_GET['theme']);
-			unset( $allowed_themes[ $_GET['theme'] ] );
-			update_site_option( 'allowedthemes', $allowed_themes );
+			WP_Theme::network_disable_theme( $_GET['theme'] );
 			wp_safe_redirect( add_query_arg( 'disabled', '1', $referer ) );
 			exit;
 		case 'enable-selected':
@@ -53,9 +50,7 @@
 				wp_safe_redirect( add_query_arg( 'error', 'none', $referer ) );
 				exit;
 			}
-			foreach ( (array) $themes as $theme )
-				$allowed_themes[ $theme ] = true;
-			update_site_option( 'allowedthemes', $allowed_themes );
+			WP_Theme::network_enable_theme( (array) $themes );
 			wp_safe_redirect( add_query_arg( 'enabled', count( $themes ), $referer ) );
 			exit;
 		case 'disable-selected':
@@ -65,9 +60,7 @@
 				wp_safe_redirect( add_query_arg( 'error', 'none', $referer ) );
 				exit;
 			}
-			foreach ( (array) $themes as $theme )
-				unset( $allowed_themes[ $theme ] );
-			update_site_option( 'allowedthemes', $allowed_themes );
+			WP_Theme::network_disable_theme( (array) $themes );
 			wp_safe_redirect( add_query_arg( 'disabled', count( $themes ), $referer ) );
 			exit;
 		case 'update-selected' :
Index: src/wp-includes/class-wp-theme.php
===================================================================
--- src/wp-includes/class-wp-theme.php	(revision 37177)
+++ src/wp-includes/class-wp-theme.php	(working copy)
@@ -1316,6 +1316,62 @@
 	}
 
 	/**
+	 * Enable a theme for all sites on the current network.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @static
+	 * @access public
+	 *
+	 * @param string|array $stylesheets Stylesheet name or array of stylesheet names.
+	 */
+	public static function network_enable_theme( $stylesheets ) {
+		if ( ! is_multisite() ) {
+			return;
+		}
+
+		if ( ! is_array( $stylesheets ) ) {
+			$stylesheets = array( $stylesheets );
+		}
+
+		$allowed_themes = get_site_option( 'allowedthemes' );
+		foreach ( $stylesheets as $stylesheet ) {
+			$allowed_themes[ $stylesheet ] = true;
+		}
+
+		update_site_option( 'allowedthemes', $allowed_themes );
+	}
+
+	/**
+	 * Disable a theme for all sites on the current network.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @static
+	 * @access public
+	 *
+	 * @param string|array $stylesheets Stylesheet name or array of stylesheet names.
+	 */
+	public static function network_disable_theme( $stylesheets ) {
+		if ( ! is_multisite() ) {
+			return;
+		}
+
+		if ( ! is_array( $stylesheets ) ) {
+			$stylesheets = array( $stylesheets );
+		}
+
+		$allowed_themes = get_site_option( 'allowedthemes' );
+		foreach ( $stylesheets as $stylesheet ) {
+			if ( isset( $allowed_themes[ $stylesheet ] ) ) {
+				unset( $allowed_themes[ $stylesheet ] );
+			}
+		}
+
+		update_site_option( 'allowedthemes', $allowed_themes );
+	}
+
+	/**
 	 * Sorts themes by name.
 	 *
 	 * @since 3.4.0
Index: tests/phpunit/tests/theme/WPTheme.php
===================================================================
--- tests/phpunit/tests/theme/WPTheme.php	(revision 37177)
+++ tests/phpunit/tests/theme/WPTheme.php	(working copy)
@@ -139,4 +139,94 @@
 		$this->assertFalse( $theme->get( 'Tags' ) );
 		$this->assertFalse( $theme->display( 'Tags' ) );
 	}
+
+
+	/**
+	 * Enable a single theme on a network.
+	 *
+	 * @ticket 30594
+	 */
+	function test_wp_theme_network_enable_single_theme() {
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( 'This test requires multisite' );
+		}
+
+		$theme = 'testtheme-1';
+		$current_allowed_themes = get_site_option( 'allowedthemes' );
+		WP_Theme::network_enable_theme( $theme );
+		$new_allowed_themes = get_site_option( 'allowedthemes' );
+		update_site_option( 'allowedthemes', $current_allowed_themes ); // reset previous value.
+		$current_allowed_themes['testtheme-1'] = true; // Add the new theme to the previous set.
+
+		$this->assertEqualSetsWithIndex( $current_allowed_themes, $new_allowed_themes );
+	}
+
+	/**
+	 * Enable multiple themes on a network.
+	 *
+	 * @ticket 30594
+	 */
+	function test_wp_theme_network_enable_multiple_themes() {
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( 'This test requires multisite' );
+		}
+
+		$themes = array( 'testtheme-2', 'testtheme-3' );
+		$current_allowed_themes = get_site_option( 'allowedthemes' );
+		WP_Theme::network_enable_theme( $themes );
+		$new_allowed_themes = get_site_option( 'allowedthemes' );
+		update_site_option( 'allowedthemes', $current_allowed_themes ); // reset previous value.
+		$current_allowed_themes = array_merge( $current_allowed_themes, array( 'testtheme-2' => true, 'testtheme-3' => true ) );
+
+		$this->assertEqualSetsWithIndex( $current_allowed_themes, $new_allowed_themes );
+	}
+
+	/**
+	 * Disable a single theme on a network.
+	 *
+	 * @ticket 30594
+	 */
+	function test_network_disable_single_theme() {
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( 'This test requires multisite' );
+		}
+
+		$current_allowed_themes = get_site_option( 'allowedthemes' );
+
+		$allowed_themes = array( 'existing-1' => true, 'existing-2' => true, 'existing-3' => true );
+		update_site_option( 'allowedthemes', $allowed_themes );
+
+		$disable_theme = 'existing-2';
+		WP_Theme::network_disable_theme( $disable_theme );
+		$new_allowed_themes = get_site_option( 'allowedthemes' );
+		update_site_option( 'allowedthemes', $current_allowed_themes ); // reset previous value.
+		unset( $allowed_themes[ $disable_theme ] ); // Remove deleted theme from initial set.
+
+		$this->assertEqualSetsWithIndex( $allowed_themes, $new_allowed_themes );
+	}
+
+	/**
+	 * Disable multiple themes on a network.
+	 *
+	 * @ticket 30594
+	 */
+	function test_network_disable_multiple_themes() {
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( 'This test requires multisite' );
+		}
+
+		$current_allowed_themes = get_site_option( 'allowedthemes' );
+
+		$allowed_themes = array( 'existing-4' => true, 'existing-5' => true, 'existing-6' => true );
+		update_site_option( 'allowedthemes', $allowed_themes );
+
+		$disable_themes = array( 'existing-4', 'existing-5' );
+		WP_Theme::network_disable_theme( $disable_themes );
+		$new_allowed_themes = get_site_option( 'allowedthemes' );
+		update_site_option( 'allowedthemes', $current_allowed_themes ); // reset previous value.
+		unset( $allowed_themes['existing-4'] );
+		unset( $allowed_themes['existing-5'] );
+
+		$this->assertEqualSetsWithIndex( $allowed_themes, $new_allowed_themes );
+	}
 }