diff --git a/Gruntfile.js b/Gruntfile.js
index cb263c8bd8..68793d0219 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -413,7 +413,7 @@ module.exports = function(grunt) {
 		},
 		cssmin: {
 			options: {
-				compatibility: 'ie7'
+				compatibility: 'ie9'
 			},
 			core: {
 				expand: true,
diff --git a/src/js/_enqueues/admin/common.js b/src/js/_enqueues/admin/common.js
index 75c77b3bac..4b287f6cd5 100644
--- a/src/js/_enqueues/admin/common.js
+++ b/src/js/_enqueues/admin/common.js
@@ -474,7 +474,6 @@ $document.ready( function() {
 		currentPage = pageInput.val(),
 		isIOS = /iPhone|iPad|iPod/.test( navigator.userAgent ),
 		isAndroid = navigator.userAgent.indexOf( 'Android' ) !== -1,
-		isIE8 = $( document.documentElement ).hasClass( 'ie8' ),
 		$adminMenuWrap = $( '#adminmenuwrap' ),
 		$wpwrap = $( '#wpwrap' ),
 		$adminmenu = $( '#adminmenu' ),
@@ -1060,7 +1059,7 @@ $document.ready( function() {
 		var windowPos = $window.scrollTop(),
 			resizing = ! event || event.type !== 'scroll';
 
-		if ( isIOS || isIE8 || $adminmenu.data( 'wp-responsive' ) ) {
+		if ( isIOS || $adminmenu.data( 'wp-responsive' ) ) {
 			return;
 		}
 
diff --git a/src/wp-admin/css/admin-menu.css b/src/wp-admin/css/admin-menu.css
index a3d8f4f262..1ac83c9ed6 100644
--- a/src/wp-admin/css/admin-menu.css
+++ b/src/wp-admin/css/admin-menu.css
@@ -382,11 +382,6 @@ div.wp-menu-image:before {
 	color: #00b9eb;
 }
 
-/* IE8 doesn't redraw the pseudo elements unless you make a change to the content, this restore the initial color after hover */
-.ie8 #adminmenu li.opensub div.wp-menu-image:before {
-	color: #a0a5aa;
-}
-
 .folded #adminmenu div.wp-menu-image {
 	width: 35px;
 	height: 30px;
diff --git a/src/wp-admin/css/colors/_admin.scss b/src/wp-admin/css/colors/_admin.scss
index ca01267a24..0354e5db27 100644
--- a/src/wp-admin/css/colors/_admin.scss
+++ b/src/wp-admin/css/colors/_admin.scss
@@ -271,9 +271,6 @@ ul#adminmenu > li.current > a.current:after {
 #adminmenu li:hover div.wp-menu-image:before,
 #adminmenu li a:focus div.wp-menu-image:before,
 #adminmenu li.opensub div.wp-menu-image:before,
-.ie8 #adminmenu li.opensub div.wp-menu-image:before {
-	color: $menu-current-icon;
-}
 
 
 /* Admin Menu: bubble */
diff --git a/src/wp-admin/css/common.css b/src/wp-admin/css/common.css
index 878df291ad..cb9be4aaae 100644
--- a/src/wp-admin/css/common.css
+++ b/src/wp-admin/css/common.css
@@ -279,10 +279,6 @@ a:focus .media-icon img,
 		outline: 1px solid transparent;
 }
 
-.ie8 a:focus {
-	outline: #5b9dd9 solid 1px;
-}
-
 #adminmenu a:focus {
 	box-shadow: none;
 	/* Only visible in Windows High Contrast mode */
@@ -1441,10 +1437,6 @@ div.error p,
 		0 0 2px 1px rgba(30, 140, 190, 0.8);
 }
 
-.ie8 .notice-dismiss:focus {
-	outline: 1px solid #5b9dd9;
-}
-
 .notice-success,
 div.updated {
 	border-left-color: #46b450;
@@ -1766,10 +1758,6 @@ form.upgrade .hint {
 	font-weight: 600;
 }
 
-.ie8 #screen-options-wrap legend {
-	color: inherit;
-}
-
 .metabox-prefs label {
 	display: inline-block;
 	padding-right: 15px;
@@ -2247,13 +2235,6 @@ h1.nav-tab-wrapper, /* Back-compat for pre-4.4 */
 	clear: both;
 }
 
-.ie8 .nav-tab-wrapper {
-	/* contain floats establishing a new block formatting context */
-	display: inline-block;
-	width: 100%;
-	vertical-align: top;
-}
-
 /*------------------------------------------------------------------------------
   26.0 - Misc
 ------------------------------------------------------------------------------*/
diff --git a/src/wp-admin/css/customize-nav-menus.css b/src/wp-admin/css/customize-nav-menus.css
index 145938252e..5ce9eb46bb 100644
--- a/src/wp-admin/css/customize-nav-menus.css
+++ b/src/wp-admin/css/customize-nav-menus.css
@@ -475,10 +475,6 @@
 	-moz-osx-font-smoothing: grayscale;
 }
 
-.ie8 .menu-item-bar .item-delete:before {
-	top: -10px;
-}
-
 .menu-item-bar .item-delete:hover,
 .menu-item-bar .item-delete:focus {
 	box-shadow: none;
diff --git a/src/wp-admin/css/dashboard.css b/src/wp-admin/css/dashboard.css
index 2784b804d0..457aa9fc19 100644
--- a/src/wp-admin/css/dashboard.css
+++ b/src/wp-admin/css/dashboard.css
@@ -38,24 +38,6 @@
 	border: none !important;
 }
 
-.ie8 #wpbody-content #dashboard-widgets .postbox-container {
-	width: 49.5%;
-}
-
-.ie8 #wpbody-content #dashboard-widgets #postbox-container-2,
-.ie8 #wpbody-content #dashboard-widgets #postbox-container-3,
-.ie8 #wpbody-content #dashboard-widgets #postbox-container-4 {
-	float: right;
-	width: 50.5%;
-}
-
-.ie8 #dashboard-widgets #postbox-container-3 .empty-container,
-.ie8 #dashboard-widgets #postbox-container-4 .empty-container {
-	border: 0 none;
-	height: 0;
-	min-height: 0;
-}
-
 #dashboard-widgets-wrap {
 	overflow: hidden;
 	margin: 0 -8px;
@@ -180,10 +162,6 @@
 	float: left;
 }
 
-.ie8 .welcome-panel .welcome-panel-column {
-	min-width: 230px;
-}
-
 .welcome-panel .welcome-panel-column:first-child {
 	width: 36%;
 }
diff --git a/src/wp-admin/css/edit.css b/src/wp-admin/css/edit.css
index 1c2b3336ca..77e6f75b06 100644
--- a/src/wp-admin/css/edit.css
+++ b/src/wp-admin/css/edit.css
@@ -635,11 +635,6 @@ form#tags-filter {
 	max-width: 100%;
 }
 
-.ie8 #poststuff .inside #parent_id,
-.ie8 #poststuff .inside #page_template {
-	width: 250px;
-}
-
 .post-attributes-label-wrapper {
 	margin-bottom: 0.5em;
 }
diff --git a/src/wp-admin/css/ie.css b/src/wp-admin/css/ie.css
deleted file mode 100644
index 00853ab7c8..0000000000
--- a/src/wp-admin/css/ie.css
+++ /dev/null
@@ -1,764 +0,0 @@
-/* Fixes for IE 7 bugs */
-
-#dashboard-widgets form .input-text-wrap input,
-#dashboard-widgets form .textarea-wrap textarea {
-	width: 99%;
-}
-
-#dashboard-widgets form #title {
-	width: 98%;
-}
-
-#wpbody-content #dashboard-widgets .postbox-container {
-	width: 49.5%;
-}
-
-#wpbody-content #dashboard-widgets #postbox-container-2,
-#wpbody-content #dashboard-widgets #postbox-container-3,
-#wpbody-content #dashboard-widgets #postbox-container-4 {
-	float: right;
-	width: 50.5%;
-}
-
-#dashboard-widgets #postbox-container-3 .empty-container,
-#dashboard-widgets #postbox-container-4 .empty-container {
-	border: 0 none;
-	height: 0;
-	min-height: 0;
-}
-
-.wp-editor-wrap .wp-editor-tools,
-.wp-editor-wrap .wp-switch-editor,
-.wp-editor-wrap .wp-editor-tabs,
-.wp-editor-wrap .wp-editor-container {
-	zoom: 100%;
-}
-
-.wp-editor-wrap .wp-editor-container textarea.wp-editor-area {
-	width: 97%;
-}
-
-#post-body.columns-2 #postbox-container-1 {
-	padding-left: 19px;
-}
-
-.welcome-panel .wp-badge {
-	position: absolute;
-}
-
-.welcome-panel .welcome-panel-column:first-child {
-	width: 35%;
-}
-
-#adminmenuback {
-	left: 0;
-	background-image: none;
-}
-
-#adminmenuwrap {
-	position: static;
-}
-
-#adminmenu {
-	position: relative;
-}
-
-#adminmenu,
-#adminmenu a {
-	cursor: pointer;
-}
-
-#adminmenu li.wp-menu-separator,
-#adminmenu li.wp-menu-separator-last {
-	font-size: 1px;
-	line-height: 1;
-}
-
-#adminmenu a.menu-top {
-	border-bottom: 0 none;
-	border-top: 1px solid #ddd;
-}
-
-#adminmenu .separator {
-	font-size: 1px;
-	line-height: 1px;
-}
-
-#adminmenu .wp-submenu {
-	left: 110px;
-}
-
-#adminmenu .wp-submenu ul {
-	margin: 0;
-}
-
-.folded #wpcontent,
-.folded #wpfooter {
-	margin-left: 170px;
-}
-
-.folded #adminmenuback,
-.folded #adminmenuwrap,
-.folded #adminmenu,
-.folded #adminmenu li.menu-top {
-	width: 150px;
-}
-
-.folded #adminmenu .wp-submenu {
-	border-top-color: transparent;
-}
-
-.folded #adminmenu .wp-menu-name {
-	display: block;
-}
-
-.folded #adminmenu .wp-submenu.sub-open,
-.folded #adminmenu .opensub .wp-submenu {
-	left: 110px;
-}
-
-.folded #adminmenu a.wp-has-current-submenu:focus + .wp-submenu,
-.folded #adminmenu .wp-has-current-submenu .wp-submenu {
-	top: -1px;
-	position: relative;
-}
-
-.folded #adminmenu .wp-has-current-submenu .wp-submenu .wp-submenu-head {
-	background-color: transparent;
-}
-
-#adminmenu .wp-submenu .wp-submenu-head {
-	border-top-color: #ddd;
-}
-
-.folded #adminmenu .wp-submenu ul {
-	margin-left: 5px;
-}
-
-#adminmenu li.menu-top {
-	margin-bottom: -2px;
-}
-
-#adminmenu .wp-menu-arrow {
-	display: none !important;
-}
-
-.js.folded #adminmenu li.menu-top {
-	display: block;
-	zoom: 100%;
-}
-
-ul#adminmenu {
-	z-index: 99;
-}
-
-#adminmenu li.menu-top a.menu-top {
-	min-width: auto;
-	width: auto;
-}
-
-#wpcontent #adminmenu li.wp-has-current-submenu a.wp-has-submenu {
-	font-style: normal;
-}
-
-#wpcontent #adminmenu .wp-submenu li {
-	padding: 0;
-}
-
-#adminmenu li.wp-has-current-submenu .wp-submenu {
-	left: -40px;
-}
-
-#adminmenu .wp-menu-image {
-	display: none !important;
-}
-
-#adminmenu a.menu-top .wp-menu-name {
-	padding-left: 8px;
-}
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-#collapse-menu {
-	line-height: 23px;
-}
-
-#wpadminbar .ab-comments-icon {
-	padding-top: 7px;
-}
-
-
-.theme-browser .theme {
-	width: 30%;
-	margin: 0 3% 4% 0;
-	cursor: auto;
-}
-
-.theme-browser .theme:hover,
-.theme-browser .theme:focus {
-	cursor: auto;
-}
-
-.theme-browser .theme .theme-screenshot {
-	height: 180px;
-}
-
-.theme-browser .theme .theme-actions {
-	position: static;
-	background-color: #e8e8e8;
-}
-
-.theme-browser .theme .more-details {
-	display: none;
-}
-
-.plugins td,
-.plugins th {
-	border-top: 1px solid #ddd;
-}
-
-table.fixed th,
-table.fixed td {
-	border-top: 1px solid #ddd;
-}
-
-#wpbody-content input.button,
-#wpbody-content input.button-primary {
-	overflow: visible;
-}
-
-#dashboard-widgets h3 a {
-	height: 14px;
-	line-height: 14px;
-}
-
-#dashboard_browser_nag {
-	color: #fff;
-}
-
-#dashboard_browser_nag .browser-icon {
-	position: relative;
-}
-
-.tablenav-pages .current-page {
-	vertical-align: middle;
-}
-
-#wpbody-content .postbox {
-	border: 1px solid #ddd;
-}
-
-#wpbody-content .postbox .hndle {
-	margin-bottom: -1px;
-}
-
-.major-publishing-actions,
-.wp-submenu,
-.wp-submenu li,
-#template,
-#template div,
-#editcat,
-#addcat {
-	zoom: 100%;
-}
-
-.wp-menu-arrow {
-	height: 28px;
-}
-
-.submitbox {
-	margin-top: 10px;
-}
-
-/* Inline Editor */
-#wpbody-content .quick-edit-row-post .inline-edit-col-left {
-	width: 39%;
-}
-
-#wpbody-content .inline-edit-row-post .inline-edit-col-center {
-	width: 19%;
-}
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-#wpbody-content .quick-edit-row-page .inline-edit-col-left {
-	width: 49%;
-}
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-#wpbody-content .bulk-edit-row .inline-edit-col-left {
-	width: 29%;
-}
-
-.inline-edit-row .submit {
-	zoom: 100%;
-}
-
-.inline-edit-row fieldset label span.title {
-	display: block;
-	float: left;
-	width: 5em;
-}
-
-.inline-edit-row fieldset label span.input-text-wrap {
-	margin-left: 0;
-	zoom: 100%;
-}
-
-#wpbody-content .inline-edit-row fieldset label span.input-text-wrap input {
-	line-height: 130%;
-}
-
-#wpbody-content .inline-edit-row .input-text-wrap input {
-	width: 95%;
-}
-
-#wpbody-content .inline-edit-row .input-text-wrap input.inline-edit-password-input {
-	width: 8em;
-}
-/* end Inline Editor */
-
-#titlediv #title {
-	width: 98%;
-}
-
-.button,
-input[type="reset"],
-input[type="button"],
-input[type="submit"] {
-	padding: 0 8px;
-	line-height: 20px;
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-}
-
-.button.button-large,
-input[type="reset"].button-large,
-input[type="button"].button-large,
-input[type="submit"].button-large {
-	padding: 0 10px;
-	line-height: 24px;
-	height: auto;
-}
-
-.button.button-small,
-input[type="reset"].button-small,
-input[type="button"].button-small,
-input[type="submit"].button-small {
-	padding: 0 6px;
-	line-height: 16px;
-	height: auto;
-}
-
-a.button {
-	margin: 1px;
-	padding: 1px 9px 2px;
-}
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-a.button.button-large {
-	padding: 1px 11px 2px;
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-a.button.button-small {
-	padding: 1px 7px 2px;
-}
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-#screen-options-wrap {
-	overflow: hidden;
-}
-
-#the-comment-list .comment-item,
-#post-status-info,
-#wpwrap,
-#wrap,
-#postdivrich,
-#postdiv,
-#poststuff,
-.metabox-holder,
-#titlediv,
-#post-body,
-#editorcontainer,
-.tablenav,
-.widget-liquid-left,
-.widget-liquid-right,
-#widgets-left,
-.widgets-sortables,
-#dragHelper,
-.widget .widget-top,
-.widget-control-actions,
-.tagchecklist,
-#col-container,
-#col-left,
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-.fileedit-sub {
-	display: block;
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-	float: right;
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-#widget-list .widget {
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-#editorcontainer #content {
-	overflow: auto;
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-	width: 98%;
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-form#template div {
-	width: 100%;
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-.wp-editor-container .quicktags-toolbar input {
-	overflow: visible;
-	padding: 0 4px;
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-#poststuff h2 {
-	font-size: 1.6em;
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-
-#poststuff .inside #parent_id,
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-.inline-edit-row #post_parent,
-.inline-edit-row select[name="page_template"] {
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-#submitdiv input,
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-	margin: 7px 10px 0 0;
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-div#dashboard-widgets {
-	padding-right: 1px;
-}
-
-.tagchecklist > li, .tagchecklist .ntdelbutton {
-	display: inline-block;
-	display: block;
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-.tagchecklist .ntdelbutton:focus .remove-tag-icon:before {
-	outline: 1px solid #5b9dd9;
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-.tablenav .button,
-.nav .button {
-	padding-top: 2px;
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-.tablenav select {
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-.tablenav .actions select {
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-.subsubsub li {
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-.widefat tr,
-.widefat th,
-.widefat thead td,
-.widefat tfoot td {
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-.widefat th input,
-.widefat thead td input,
-.widefat tfoot td input {
-	margin: 0 0 0 5px;
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-.widefat thead .check-column,
-.widefat tfoot .check-column {
-	padding-top: 6px;
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-.widefat tbody th.check-column,
-.media.widefat tbody th.check-column {
-	padding: 4px 0 0;
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-.widefat {
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-.tablenav a.button {
-	display: inline-block;
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-.inactive-sidebar .widgets-sortables {
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-#available-widgets .widget-holder {
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-#widgets-left .inactive {
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-.widget-liquid-right .widget,
-.inactive-sidebar .widget {
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-.inactive-sidebar .widget {
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-.imgedit-submit {
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-#nav-menus-frame,
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-.menu li {
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-.menu li {
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-.menu li.sortable-placeholder {
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-.available-theme {
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-.available-theme ul {
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-.available-theme .action-links li {
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-.about-wrap .three-col.about-updates .col-2 {
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-.about-wrap .about-password-meter input {
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-.revisions-tooltip {
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-.revisions.pinned .revisions-controls {
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-input[type="password"],
-.login form .input {
-	font-family: sans-serif;
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-.mce-btn i.mce-i-bold,
-.mce-btn i.mce-i-italic,
-.mce-btn i.mce-i-bullist,
-.mce-btn i.mce-i-numlist,
-.mce-btn i.mce-i-blockquote,
-.mce-btn i.mce-i-alignleft,
-.mce-btn i.mce-i-aligncenter,
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-.mce-btn i.mce-i-link,
-.mce-btn i.mce-i-unlink,
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-.mce-btn i.mce-i-underline,
-.mce-btn i.mce-i-alignjustify,
-.mce-btn i.mce-i-forecolor,
-.mce-btn i.mce-i-pastetext,
-.mce-btn i.mce-i-pasteword,
-.mce-btn i.mce-i-removeformat,
-.mce-btn i.mce-i-charmap,
-.mce-btn i.mce-i-outdent,
-.mce-btn i.mce-i-indent,
-.mce-btn i.mce-i-undo,
-.mce-btn i.mce-i-redo,
-.mce-btn i.mce-i-help,
-.mce-btn i.mce-i-wp_help,
-.mce-btn i.mce-i-wp-media-library,
-.mce-btn i.mce-i-ltr,
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-.mce-btn i.mce-i-hr,
-.mce-close {
-	font-family: tinymce, Arial;
-	font-style: normal;
-	font-weight: 400;
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-	font-size: 16px;
-	margin-left: 0;
-	padding-right: 0;
-}
-
-.mce-btn i.mce-i-wp_fullscreen,
-.qt-fullscreen {
-	-ie7-icon: "\e023";
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-
-.mce-btn i.mce-i-wp_more,
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-	-ie7-icon: "\e027";
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-.mce-btn i.mce-i-wp_adv {
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-.mce-btn i.mce-i-help,
-.mce-btn i.mce-i-wp_help {
-	-ie7-icon: "\e016";
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-
-
-/* IE6 leftovers */
-* html .row-actions {
-	visibility: visible;
-}
-
-* html div.widget-liquid-left,
-* html div.widget-liquid-right {
-	display: block;
-	position: relative;
-}
-
-* html #editorcontainer {
-	padding: 0;
-}
-
-* html #poststuff h2 {
-	margin-left: 0;
-}
-
-* html .stuffbox,
-* html .stuffbox input,
-* html .stuffbox textarea {
-	border: 1px solid #ddd;
-}
-
-* html div.widget-liquid-left {
-	width: 99%;
-}
-
-* html .widgets-sortables {
-	height: 50px;
-}
-
-* html a#content_resize {
-	right: -2px;
-}
-
-* html .widget-title h4 {
-	width: 205px;
-}
-
-* html #removing-widget .in-widget-title {
-	display: none;
-}
-
-* html .media-item .pinkynail {
-	height: 32px;
-	width: 40px;
-}
-
-* html .describe .field input.text,
-* html .describe .field textarea {
-	width: 440px;
-}
-
-* html input {
-	border: 1px solid #ddd;
-}
-
-* html .edit-box {
-	display: inline;
-}
-
-* html .postbox-container .meta-box-sortables {
-	height: 300px;
-}
-
-* html #wpbody-content #screen-options-link-wrap {
-	display: inline-block;
-	width: 150px;
-	text-align: center;
-}
-
-* html #wpbody-content #contextual-help-link-wrap {
-	display: inline-block;
-	width: 100px;
-	text-align: center;
-}
-
-* html #adminmenu {
-	margin-left: -80px;
-}
-
-* html .folded #adminmenu {
-	margin-left: -22px;
-}
-
-* html #wpcontent #adminmenu li.menu-top {
-	display: inline;
-	padding: 0;
-	margin: 0;
-}
-
-* html #wpfooter {
-	margin: 0;
-}
-
-* html #adminmenu div.wp-menu-image {
-	height: 29px;
-}
diff --git a/src/wp-admin/css/install.css b/src/wp-admin/css/install.css
index a9a2cdf85f..7f0f48cc32 100644
--- a/src/wp-admin/css/install.css
+++ b/src/wp-admin/css/install.css
@@ -30,10 +30,6 @@ a:focus {
 		0 0 2px 1px rgba(30, 140, 190, 0.8);
 }
 
-.ie8 a:focus {
-	outline: #5b9dd9 solid 1px;
-}
-
 h1, h2 {
 	border-bottom: 1px solid #ddd;
 	clear: both;
diff --git a/src/wp-admin/css/list-tables.css b/src/wp-admin/css/list-tables.css
index 3e55bb2d0e..f621aef2ab 100644
--- a/src/wp-admin/css/list-tables.css
+++ b/src/wp-admin/css/list-tables.css
@@ -62,13 +62,6 @@
 	text-align: center;
 }
 
-.ie8 .column-response .comment-count-no-comments,
-.ie8 .column-response .comment-count-approved,
-.ie8 .column-comments .comment-count-no-comments,
-.ie8 .column-comments .comment-count-approved {
-	min-width: 0;
-}
-
 .column-response .post-com-count-no-comments:after,
 .column-response .post-com-count-approved:after,
 .column-comments .post-com-count-no-comments:after,
@@ -513,10 +506,6 @@ th.asc a:focus span.sorting-indicator:before {
 		0 0 2px 1px rgba(30, 140, 190, 0.8);
 }
 
-.ie8 .wp-list-table .toggle-row:focus:before {
-	outline: #5b9dd9 solid 1px;
-}
-
 .wp-list-table .toggle-row:active {
 	box-shadow: none;
 }
@@ -1080,11 +1069,6 @@ ul.cat-checklist {
 	max-width: 80%;
 }
 
-.ie8 .inline-edit-row #post_parent,
-.ie8 .inline-edit-row select[name="page_template"] {
-	width: 250px;
-}
-
 .quick-edit-row-post fieldset label.inline-edit-status {
 	float: left;
 }
diff --git a/src/wp-admin/css/revisions.css b/src/wp-admin/css/revisions.css
index 16b8278aa3..4b3a6e48d8 100644
--- a/src/wp-admin/css/revisions.css
+++ b/src/wp-admin/css/revisions.css
@@ -79,7 +79,6 @@
 	top: 50%;
 	top: calc( 50% - 10px );
 	transition: opacity 0.5s;
-	filter: alpha(opacity=0); /* ie8 and earlier */
 }
 
 body.folded .revisions .loading-indicator {
@@ -94,7 +93,6 @@ body.folded .revisions .loading-indicator {
 
 .revisions.loading .loading-indicator {
 	opacity: 1;
-	filter: alpha(opacity=100); /* ie8 and earlier */
 }
 
 .revisions .diff {
@@ -103,7 +101,6 @@ body.folded .revisions .loading-indicator {
 
 .revisions.loading .diff {
 	opacity: 0.5;
-	filter: alpha(opacity=50); /* ie8 and earlier */
 }
 
 .revisions.diff-error .diff {
@@ -385,16 +382,6 @@ table.diff .diff-addedline ins {
 	right: 20px;
 }
 
-.ie8 .revisions-tooltip-arrow > span {
-	left: 15px;
-	top: -25px;
-	-ms-filter: "progid:DXImageTransform.Microsoft.Matrix(SizingMethod='auto expand', M11=0.7071067811865476, M12=-0.7071067811865475, M21=0.7071067811865475, M22=0.7071067811865476)";
-}
-
-.ie8 .revisions-tooltip.flipped .revisions-tooltip-arrow > span {
-	right: 25px;
-}
-
 .revisions-tooltip,
 .revisions-tooltip-arrow > span {
 	border: 1px solid #ddd;
diff --git a/src/wp-admin/css/themes.css b/src/wp-admin/css/themes.css
index 3bc589c18a..279e4d1283 100644
--- a/src/wp-admin/css/themes.css
+++ b/src/wp-admin/css/themes.css
@@ -61,11 +61,6 @@ body.js .theme-browser.search-loading {
 	box-sizing: border-box;
 }
 
-.ie8 .theme-browser .theme {
-	width: 30%;
-	margin: 0 3% 4% 0;
-}
-
 .theme-browser .theme:nth-child(3n) {
 	margin-right: 0;
 }
@@ -504,10 +499,6 @@ body.folded .theme-browser ~ .theme-overlay .theme-wrap {
 	border-top: 1px solid #eee;
 }
 
-.ie8 .theme-overlay .theme-actions {
-	border: 1px solid #eee;
-}
-
 .theme-overlay .theme-actions a {
 	margin-right: 5px;
 	margin-bottom: 5px;
diff --git a/src/wp-admin/includes/template.php b/src/wp-admin/includes/template.php
index c140849f6e..14c77f2fea 100644
--- a/src/wp-admin/includes/template.php
+++ b/src/wp-admin/includes/template.php
@@ -2442,30 +2442,14 @@ function _wp_admin_html_begin() {
 
 	?>
 <!DOCTYPE html>
-<!--[if IE 8]>
-<html xmlns="http://www.w3.org/1999/xhtml" class="ie8 <?php echo $admin_html_class; ?>"
-	<?php
-	/**
-	 * Fires inside the HTML tag in the admin header.
-	 *
-	 * @since 2.2.0
-	 */
-	do_action( 'admin_xml_ns' );
-
-	language_attributes();
-	?>
-	>
-<![endif]-->
-<!--[if !(IE 8) ]><!-->
 <html xmlns="http://www.w3.org/1999/xhtml" class="<?php echo $admin_html_class; ?>"
 	<?php
 	/** This action is documented in wp-admin/includes/template.php */
 	do_action( 'admin_xml_ns' );
 
-	language_attributes();
+		language_attributes();
 	?>
-	>
-<!--<![endif]-->
+>
 <head>
 <meta http-equiv="Content-Type" content="<?php bloginfo( 'html_type' ); ?>; charset=<?php echo get_option( 'blog_charset' ); ?>" />
 	<?php
diff --git a/src/wp-includes/class-wp-admin-bar.php b/src/wp-includes/class-wp-admin-bar.php
index 063aa32a39..dd2f4b4538 100644
--- a/src/wp-includes/class-wp-admin-bar.php
+++ b/src/wp-includes/class-wp-admin-bar.php
@@ -434,11 +434,7 @@ class WP_Admin_Bar {
 		// We have to do this here since admin bar shows on the front end.
 		$class = 'nojq nojs';
 		if ( $is_IE ) {
-			if ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 7' ) ) {
-				$class .= ' ie7';
-			} elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 8' ) ) {
-				$class .= ' ie8';
-			} elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 9' ) ) {
+			if ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 9' ) ) {
 				$class .= ' ie9';
 			}
 		} elseif ( wp_is_mobile() ) {
diff --git a/src/wp-includes/css/admin-bar.css b/src/wp-includes/css/admin-bar.css
index d0f4457e7a..5fbed57749 100644
--- a/src/wp-includes/css/admin-bar.css
+++ b/src/wp-includes/css/admin-bar.css
@@ -149,12 +149,6 @@ html:lang(he-il) .rtl #wpadminbar * {
 	float: none;
 }
 
-#wpadminbar.ie7 .menupop .ab-sub-wrapper,
-#wpadminbar.ie7 .shortlink-input {
-	top: 32px;
-	left: 0;
-}
-
 #wpadminbar .ab-top-menu > .menupop > .ab-sub-wrapper {
 	min-width: 100%;
 }
@@ -422,10 +416,6 @@ html:lang(he-il) .rtl #wpadminbar * {
 	min-width: 270px;
 }
 
-#wpadminbar.ie8 #wp-admin-bar-my-account.with-avatar .ab-item {
-	white-space: nowrap;
-}
-
 #wpadminbar #wp-admin-bar-user-actions > li {
 	margin-left: 16px;
 	margin-right: 16px;
@@ -489,11 +479,6 @@ html:lang(he-il) .rtl #wpadminbar * {
 	display: inline;
 }
 
-#wpadminbar.ie8 #wp-admin-bar-my-account.with-avatar > .ab-empty-item img,
-#wpadminbar.ie8 #wp-admin-bar-my-account.with-avatar > a img {
-	width: auto;
-}
-
 /**
  * WP Logo
  */
@@ -606,10 +591,7 @@ html:lang(he-il) .rtl #wpadminbar * {
 /**
  * Search
  */
-#wpadminbar.ie8 #wp-admin-bar-search {
-	display: block;
-	min-width: 32px;
-}
+
 #wpadminbar #wp-admin-bar-search .ab-item {
 	padding: 0;
 	background: transparent;
@@ -670,26 +652,6 @@ html:lang(he-il) .rtl #wpadminbar * {
 	border: 0;
 }
 
-#wpadminbar.ie7 > #wp-toolbar > #wp-admin-bar-top-secondary > #wp-admin-bar-search #adminbarsearch input.adminbar-input {
-	margin-top: 3px;
-	width: 120px;
-}
-
-#wpadminbar.ie8 > #wp-toolbar > #wp-admin-bar-top-secondary > #wp-admin-bar-search #adminbarsearch input.adminbar-input {
-	/* IE8 z-index bug with transparent / empty elements - fill in with an encoded transparent GIF */
-	background: transparent 0 0 repeat scroll url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
-}
-
-/* IE8 doesn't redraw the pseudo elements unless you make a change to the content */
-#wpadminbar.ie8 #adminbarsearch.adminbar-focused:before {
-	content: "\f179 "; /* extra space */
-}
-
-#wpadminbar.ie8 > #wp-toolbar > #wp-admin-bar-top-secondary > #wp-admin-bar-search #adminbarsearch input.adminbar-input:focus {
-	background: #fff;
-	z-index: -1;
-}
-
 #wpadminbar #adminbarsearch .adminbar-button {
 	display: none;
 }
diff --git a/src/wp-includes/css/buttons.css b/src/wp-includes/css/buttons.css
index 86844ddde0..c20927ee64 100644
--- a/src/wp-includes/css/buttons.css
+++ b/src/wp-includes/css/buttons.css
@@ -233,9 +233,6 @@ TABLE OF CONTENTS:
 	background: transparent !important;
 }
 
-.ie8 .wp-core-ui .button-link:focus {
-	outline: #5b9dd9 solid 1px;
-}
 
 /* ----------------------------------------------------------------------------
   3.0 - Primary Button Style
diff --git a/src/wp-includes/media-template.php b/src/wp-includes/media-template.php
index 87aa052171..9e349d66bf 100644
--- a/src/wp-includes/media-template.php
+++ b/src/wp-includes/media-template.php
@@ -158,9 +158,6 @@ function wp_underscore_video_template() {
 function wp_print_media_templates() {
 	global $is_IE;
 	$class = 'media-modal wp-core-ui';
-	if ( $is_IE && strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 7' ) !== false ) {
-		$class .= ' ie7';
-	}
 
 	$alt_text_description = sprintf(
 		/* translators: 1: Link to tutorial, 2: Additional link attributes, 3: Accessibility text. */
diff --git a/src/wp-includes/theme.php b/src/wp-includes/theme.php
index 03264225fe..52eb27b178 100644
--- a/src/wp-includes/theme.php
+++ b/src/wp-includes/theme.php
@@ -3316,7 +3316,7 @@ function wp_customize_url( $stylesheet = '' ) {
  * to the body tag by default.
  *
  * @since 3.4.0
- * @since 4.7.0 Support for IE8 and below is explicitly removed via conditional comments.
+ * @since 5.5.0 IE8 and older are no longer supported.
  */
 function wp_customize_support_script() {
 	$admin_origin = parse_url( admin_url() );
@@ -3324,28 +3324,21 @@ function wp_customize_support_script() {
 	$cross_domain = ( strtolower( $admin_origin['host'] ) != strtolower( $home_origin['host'] ) );
 	$type_attr    = current_theme_supports( 'html5', 'script' ) ? '' : ' type="text/javascript"';
 	?>
-	<!--[if lte IE 8]>
-		<script<?php echo $type_attr; ?>>
-			document.body.className = document.body.className.replace( /(^|\s)(no-)?customize-support(?=\s|$)/, '' ) + ' no-customize-support';
-		</script>
-	<![endif]-->
-	<!--[if gte IE 9]><!-->
-		<script<?php echo $type_attr; ?>>
-			(function() {
-				var request, b = document.body, c = 'className', cs = 'customize-support', rcs = new RegExp('(^|\\s+)(no-)?'+cs+'(\\s+|$)');
-
-		<?php	if ( $cross_domain ) : ?>
-				request = (function(){ var xhr = new XMLHttpRequest(); return ('withCredentials' in xhr); })();
-		<?php	else : ?>
-				request = true;
-		<?php	endif; ?>
-
-				b[c] = b[c].replace( rcs, ' ' );
-				// The customizer requires postMessage and CORS (if the site is cross domain).
-				b[c] += ( window.postMessage && request ? ' ' : ' no-' ) + cs;
-			}());
-		</script>
-	<!--<![endif]-->
+	<script<?php echo $type_attr; ?>>
+		(function() {
+			var request, b = document.body, c = 'className', cs = 'customize-support', rcs = new RegExp('(^|\\s+)(no-)?'+cs+'(\\s+|$)');
+
+	<?php	if ( $cross_domain ) : ?>
+			request = (function(){ var xhr = new XMLHttpRequest(); return ('withCredentials' in xhr); })();
+	<?php	else : ?>
+			request = true;
+	<?php	endif; ?>
+
+			b[c] = b[c].replace( rcs, ' ' );
+			// The customizer requires postMessage and CORS (if the site is cross domain).
+			b[c] += ( window.postMessage && request ? ' ' : ' no-' ) + cs;
+		}());
+	</script>
 	<?php
 }
 
diff --git a/src/wp-login.php b/src/wp-login.php
index 0b552ef326..93a1faa0d3 100644
--- a/src/wp-login.php
+++ b/src/wp-login.php
@@ -86,12 +86,7 @@ function login_header( $title = 'Log In', $message = '', $wp_error = null ) {
 	$login_title = apply_filters( 'login_title', $login_title, $title );
 
 	?><!DOCTYPE html>
-	<!--[if IE 8]>
-		<html xmlns="http://www.w3.org/1999/xhtml" class="ie8" <?php language_attributes(); ?>>
-	<![endif]-->
-	<!--[if !(IE 8) ]><!-->
-		<html xmlns="http://www.w3.org/1999/xhtml" <?php language_attributes(); ?>>
-	<!--<![endif]-->
+	<html xmlns="http://www.w3.org/1999/xhtml" <?php language_attributes(); ?>>
 	<head>
 	<meta http-equiv="Content-Type" content="<?php bloginfo( 'html_type' ); ?>; charset=<?php bloginfo( 'charset' ); ?>" />
 	<title><?php echo $login_title; ?></title>
