Index: src/wp-admin/css/common.css
===================================================================
--- src/wp-admin/css/common.css	(revision 37358)
+++ src/wp-admin/css/common.css	(working copy)
@@ -215,7 +215,7 @@
 body {
 	background: #f1f1f1;
 	color: #444;
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 13px;
 	line-height: 1.4em;
 	min-width: 600px;
Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 37358)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -1219,7 +1219,7 @@
 	border-bottom: 1px solid #ddd;
 	clear: both;
 	color: #666;
-	font: 24px "Open Sans", sans-serif;
+	font: 24px -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	margin: 30px 0 0 0;
 	padding: 0;
 	padding-bottom: 7px;
Index: src/wp-admin/css/dashboard.css
===================================================================
--- src/wp-admin/css/dashboard.css	(revision 37358)
+++ src/wp-admin/css/dashboard.css	(working copy)
@@ -951,8 +951,6 @@
 	color: #fff;
 }
 
-/* Make the browser nags easier to read with Open Sans */
-
 #dashboard_browser_nag h2.hndle {
 	border: none;
 	font-weight: 600;
Index: src/wp-admin/css/install.css
===================================================================
--- src/wp-admin/css/install.css	(revision 37358)
+++ src/wp-admin/css/install.css	(working copy)
@@ -6,7 +6,7 @@
 body {
 	background: #fff;
 	color: #444;
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	margin: 140px auto 25px;
 	padding: 20px 20px 10px 20px;
 	max-width: 700px;
@@ -132,7 +132,7 @@
 }
 textarea {
 	border: 1px solid #ddd;
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif
 	width: 100%;
 	-webkit-box-sizing: border-box;
 	-moz-box-sizing: border-box;
@@ -181,7 +181,7 @@
 
 input,
 submit {
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 }
 
 .form-table input[type=text],
Index: src/wp-admin/css/login.css
===================================================================
--- src/wp-admin/css/login.css	(revision 37358)
+++ src/wp-admin/css/login.css	(working copy)
@@ -12,7 +12,7 @@
 	background: #f1f1f1;
 	min-width: 0;
 	color: #444;
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 13px;
 	line-height: 1.4em;
 }
Index: src/wp-admin/css/press-this-editor.css
===================================================================
--- src/wp-admin/css/press-this-editor.css	(revision 37358)
+++ src/wp-admin/css/press-this-editor.css	(working copy)
@@ -77,7 +77,7 @@
 */
 body {
 	color: #404040;
-	font-family: "Open Sans", Helvetica, Arial, sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 20px;
 	font-weight: 400;
 	line-height: 1.6;
Index: src/wp-admin/css/press-this.css
===================================================================
--- src/wp-admin/css/press-this.css	(revision 37358)
+++ src/wp-admin/css/press-this.css	(working copy)
@@ -294,7 +294,7 @@
 select,
 textarea {
 	color: #404040;
-	font-family: "Open Sans", Helvetica, Arial, sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 20px;
 	font-weight: 400;
 	line-height: 1.6;
Index: src/wp-admin/includes/class-wp-press-this.php
===================================================================
--- src/wp-admin/includes/class-wp-press-this.php	(revision 37358)
+++ src/wp-admin/includes/class-wp-press-this.php	(working copy)
@@ -793,36 +793,7 @@
 			$press_this = str_replace( '.css', '-rtl.css', $press_this );
 		}
 
-		$open_sans_font_url = '';
-
-		/* translators: If there are characters in your language that are not supported
-		 * by Open Sans, translate this to 'off'. Do not translate into your own language.
-		 */
-		if ( 'off' !== _x( 'on', 'Open Sans font: on or off' ) ) {
-			$subsets = 'latin,latin-ext';
-
-			/* translators: To add an additional Open Sans character subset specific to your language,
-			 * translate this to 'greek', 'cyrillic' or 'vietnamese'. Do not translate into your own language.
-			 */
-			$subset = _x( 'no-subset', 'Open Sans font: add new subset (greek, cyrillic, vietnamese)' );
-
-			if ( 'cyrillic' == $subset ) {
-				$subsets .= ',cyrillic,cyrillic-ext';
-			} elseif ( 'greek' == $subset ) {
-				$subsets .= ',greek,greek-ext';
-			} elseif ( 'vietnamese' == $subset ) {
-				$subsets .= ',vietnamese';
-			}
-
-			$query_args = array(
-				'family' => urlencode( 'Open Sans:400italic,700italic,400,600,700' ),
-				'subset' => urlencode( $subsets ),
-			);
-
-			$open_sans_font_url = ',' . add_query_arg( $query_args, 'https://fonts.googleapis.com/css' );
-		}
-
-		return $styles . $press_this . $open_sans_font_url;
+		return $styles . $press_this;
 	}
 
 	/**
Index: src/wp-includes/css/admin-bar.css
===================================================================
--- src/wp-includes/css/admin-bar.css	(revision 37358)
+++ src/wp-includes/css/admin-bar.css	(working copy)
@@ -7,7 +7,7 @@
 	text-shadow: none;
 	text-transform: none;
 	letter-spacing: normal;
-	font: normal 13px/32px "Open Sans", sans-serif;
+	font: normal 13px/32px -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	-webkit-border-radius: 0;
 	border-radius: 0;
 	-webkit-box-sizing: content-box;
@@ -79,7 +79,7 @@
 #wpadminbar {
 	direction: ltr;
 	color: #ccc;
-	font: normal 13px/32px "Open Sans", sans-serif;
+	font: normal 13px/32px -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	height: 32px;
 	position: fixed;
 	top: 0;
@@ -618,7 +618,7 @@
 #wpadminbar > #wp-toolbar > #wp-admin-bar-top-secondary > #wp-admin-bar-search #adminbarsearch input.adminbar-input {
 	position: relative;
 	z-index: 30;
-	font: 13px/24px "Open Sans", sans-serif;
+	font: 13px/24px -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	height: 24px;
 	width: 24px;
 	max-width: none;
@@ -798,7 +798,7 @@
 	}
 
 	#wpadminbar * {
-		font: normal 14px/32px "Open Sans", sans-serif;
+		font: normal 14px/32px -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif, sans-serif;
 	}
 
 	#wpadminbar .quicklinks > ul > li > a,
Index: src/wp-includes/css/editor.css
===================================================================
--- src/wp-includes/css/editor.css	(revision 37358)
+++ src/wp-includes/css/editor.css	(working copy)
@@ -1109,7 +1109,8 @@
 	background: #ebebeb;
 	color: #666;
 	cursor: pointer;
-	font: 13px/19px "Open Sans", sans-serif;
+	font-size: 13px;
+	line-height: 19px;
 	height: 20px;
 	margin: 5px 0 0 5px;
 	padding: 3px 8px 4px;
Index: src/wp-includes/css/media-views.css
===================================================================
--- src/wp-includes/css/media-views.css	(revision 37358)
+++ src/wp-includes/css/media-views.css	(working copy)
@@ -17,7 +17,7 @@
 
 .media-modal,
 .media-frame {
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 12px;
 	-webkit-overflow-scrolling: touch;
 }
@@ -80,7 +80,7 @@
 .media-frame input[type="url"],
 .media-frame textarea,
 .media-frame select {
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	font-size: 12px;
 	border-width: 1px;
 	border-style: solid;
@@ -807,7 +807,7 @@
 	padding: 4px;
 	font-size: 13px;
 	color: #444;
-	font-family: "Open Sans", sans-serif;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	-webkit-appearance: none;
 }
 
Index: src/wp-includes/css/wp-embed-template.css
===================================================================
--- src/wp-includes/css/wp-embed-template.css	(revision 37358)
+++ src/wp-includes/css/wp-embed-template.css	(working copy)
@@ -59,7 +59,7 @@
 
 .wp-embed {
 	padding: 25px;
-	font: 400 14px/1.5 'Open Sans', sans-serif;
+	font: 400 14px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	color: #82878c;
 	background: white;
 	border: 1px solid #e5e5e5;
@@ -307,7 +307,7 @@
 	height: 28px;
 	margin: 0 0 10px 0;
 	padding: 0 5px;
-	font: 400 14px/1.5 'Open Sans', sans-serif;
+	font: 400 14px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 	resize: none;
 	cursor: text;
 }
Index: src/wp-includes/embed.php
===================================================================
--- src/wp-includes/embed.php	(revision 37358)
+++ src/wp-includes/embed.php	(working copy)
@@ -877,7 +877,6 @@
  * @since 4.4.0
  */
 function enqueue_embed_scripts() {
-	wp_enqueue_style( 'open-sans' );
 	wp_enqueue_style( 'wp-embed-template-ie' );
 
 	/**
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 37358)
+++ src/wp-includes/functions.php	(working copy)
@@ -2667,7 +2667,7 @@
 		body {
 			background: #fff;
 			color: #444;
-			font-family: "Open Sans", sans-serif;
+			font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen-Sans", "Ubuntu", "Cantarell", "Helvetica Neue", sans-serif;
 			margin: 2em auto;
 			padding: 1em 2em;
 			max-width: 700px;
@@ -2678,7 +2678,7 @@
 			border-bottom: 1px solid #dadada;
 			clear: both;
 			color: #666;
-			font: 24px "Open Sans", sans-serif;
+			font-size: 24px;
 			margin: 30px 0 0 0;
 			padding: 0;
 			padding-bottom: 7px;
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 37358)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -697,31 +697,6 @@
 	$styles->text_direction = function_exists( 'is_rtl' ) && is_rtl() ? 'rtl' : 'ltr';
 	$styles->default_dirs = array('/wp-admin/', '/wp-includes/css/');
 
-	$open_sans_font_url = '';
-
-	/* translators: If there are characters in your language that are not supported
-	 * by Open Sans, translate this to 'off'. Do not translate into your own language.
-	 */
-	if ( 'off' !== _x( 'on', 'Open Sans font: on or off' ) ) {
-		$subsets = 'latin,latin-ext';
-
-		/* translators: To add an additional Open Sans character subset specific to your language,
-		 * translate this to 'greek', 'cyrillic' or 'vietnamese'. Do not translate into your own language.
-		 */
-		$subset = _x( 'no-subset', 'Open Sans font: add new subset (greek, cyrillic, vietnamese)' );
-
-		if ( 'cyrillic' == $subset ) {
-			$subsets .= ',cyrillic,cyrillic-ext';
-		} elseif ( 'greek' == $subset ) {
-			$subsets .= ',greek,greek-ext';
-		} elseif ( 'vietnamese' == $subset ) {
-			$subsets .= ',vietnamese';
-		}
-
-		// Hotlink Open Sans, for now
-		$open_sans_font_url = "https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,300,400,600&subset=$subsets";
-	}
-
 	// Register a stylesheet for the selected admin color scheme.
 	$styles->add( 'colors', true, array( 'wp-admin', 'buttons' ) );
 
@@ -743,15 +718,15 @@
 	$styles->add( 'site-icon',           "/wp-admin/css/site-icon$suffix.css" );
 	$styles->add( 'l10n',                "/wp-admin/css/l10n$suffix.css" );
 
-	$styles->add( 'wp-admin', false, array( 'open-sans', 'dashicons', 'common', 'forms', 'admin-menu', 'dashboard', 'list-tables', 'edit', 'revisions', 'media', 'themes', 'about', 'nav-menus', 'widgets', 'site-icon', 'l10n' ) );
+	$styles->add( 'wp-admin', false, array( 'dashicons', 'common', 'forms', 'admin-menu', 'dashboard', 'list-tables', 'edit', 'revisions', 'media', 'themes', 'about', 'nav-menus', 'widgets', 'site-icon', 'l10n' ) );
 
-	$styles->add( 'login',               "/wp-admin/css/login$suffix.css", array( 'open-sans', 'dashicons', 'buttons', 'forms', 'l10n' ) );
-	$styles->add( 'install',             "/wp-admin/css/install$suffix.css", array( 'open-sans', 'buttons' ) );
+	$styles->add( 'login',               "/wp-admin/css/login$suffix.css", array( 'dashicons', 'buttons', 'forms', 'l10n' ) );
+	$styles->add( 'install',             "/wp-admin/css/install$suffix.css", array( 'buttons' ) );
 	$styles->add( 'wp-color-picker',     "/wp-admin/css/color-picker$suffix.css" );
 	$styles->add( 'customize-controls',  "/wp-admin/css/customize-controls$suffix.css", array( 'wp-admin', 'colors', 'ie', 'imgareaselect' ) );
 	$styles->add( 'customize-widgets',   "/wp-admin/css/customize-widgets$suffix.css", array( 'wp-admin', 'colors' ) );
 	$styles->add( 'customize-nav-menus', "/wp-admin/css/customize-nav-menus$suffix.css", array( 'wp-admin', 'colors' ) );
-	$styles->add( 'press-this',          "/wp-admin/css/press-this$suffix.css", array( 'open-sans', 'buttons' ) );
+	$styles->add( 'press-this',          "/wp-admin/css/press-this$suffix.css", array( 'buttons' ) );
 
 	$styles->add( 'ie', "/wp-admin/css/ie$suffix.css" );
 	$styles->add_data( 'ie', 'conditional', 'lte IE 7' );
@@ -759,10 +734,9 @@
 	// Common dependencies
 	$styles->add( 'buttons',   "/wp-includes/css/buttons$suffix.css" );
 	$styles->add( 'dashicons', "/wp-includes/css/dashicons$suffix.css" );
-	$styles->add( 'open-sans', $open_sans_font_url );
 
 	// Includes CSS
-	$styles->add( 'admin-bar',            "/wp-includes/css/admin-bar$suffix.css", array( 'open-sans', 'dashicons' ) );
+	$styles->add( 'admin-bar',            "/wp-includes/css/admin-bar$suffix.css", array( 'dashicons' ) );
 	$styles->add( 'wp-auth-check',        "/wp-includes/css/wp-auth-check$suffix.css", array( 'dashicons' ) );
 	$styles->add( 'editor-buttons',       "/wp-includes/css/editor$suffix.css", array( 'dashicons' ) );
 	$styles->add( 'media-views',          "/wp-includes/css/media-views$suffix.css", array( 'buttons', 'dashicons', 'wp-mediaelement' ) );