diff --git a/package.json b/package.json
index 08f92ac6d8..d69cc7847f 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,6 @@
 	"license": "GPL-2.0-or-later",
 	"browserslist": [
 		"> 1%",
-		"ie >= 11",
 		"last 1 Android versions",
 		"last 1 ChromeAndroid versions",
 		"last 2 Chrome versions",
diff --git a/src/wp-admin/css/about.css b/src/wp-admin/css/about.css
index ca72176592..a51f2753f7 100644
--- a/src/wp-admin/css/about.css
+++ b/src/wp-admin/css/about.css
@@ -85,17 +85,14 @@
 }
 
 .about__container .is-vertically-aligned-top {
-	-ms-grid-row-align: start;
 	align-self: start;
 }
 
 .about__container .is-vertically-aligned-center {
-	-ms-grid-row-align: center;
 	align-self: center;
 }
 
 .about__container .is-vertically-aligned-bottom {
-	-ms-grid-row-align: end;
 	align-self: end;
 }
 
@@ -218,7 +215,6 @@
 .about__section.has-3-columns,
 .about__section.has-4-columns,
 .about__section.has-overlap-style {
-	display: -ms-grid;
 	display: grid;
 }
 
@@ -227,93 +223,76 @@
 }
 
 .about__section.has-2-columns {
-	-ms-grid-columns: 1fr 1fr;
 	grid-template-columns: 1fr 1fr;
 }
 
 .about__section.has-2-columns.is-wider-right {
-	-ms-grid-columns: 1fr 2fr;
 	grid-template-columns: 1fr 2fr;
 }
 
 .about__section.has-2-columns.is-wider-left {
-	-ms-grid-columns: 2fr 1fr;
 	grid-template-columns: 2fr 1fr;
 }
 
 .about__section.has-2-columns .is-section-header {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 	-ms-grid-column-span: 2;
 	grid-column-end: span 2;
 }
 
 .about__section.has-2-columns .column:nth-of-type(2n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about__section.has-2-columns .column:nth-of-type(2n) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about__section.has-3-columns {
-	-ms-grid-columns: (1fr)[3];
 	grid-template-columns: repeat(3, 1fr);
 }
 
 .about__section.has-3-columns .is-section-header {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 	-ms-grid-column-span: 3;
 	grid-column-end: span 3;
 }
 
 .about__section.has-3-columns .column:nth-of-type(3n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about__section.has-3-columns .column:nth-of-type(3n+2) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about__section.has-3-columns .column:nth-of-type(3n) {
-	-ms-grid-column: 3;
 	grid-column-start: 3;
 }
 
 .about__section.has-4-columns {
-	-ms-grid-columns: (1fr)[4];
 	grid-template-columns: repeat(4, 1fr);
 }
 
 .about__section.has-4-columns .is-section-header {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 	-ms-grid-column-span: 4;
 	grid-column-end: span 4;
 }
 
 .about__section.has-4-columns .column:nth-of-type(4n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about__section.has-4-columns .column:nth-of-type(4n+2) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about__section.has-4-columns .column:nth-of-type(4n+3) {
-	-ms-grid-column: 3;
 	grid-column-start: 3;
 }
 
 .about__section.has-4-columns .column:nth-of-type(4n) {
-	-ms-grid-column: 4;
 	grid-column-start: 4;
 }
 
@@ -322,29 +301,24 @@
 .about__section.has-3-columns .is-section-header ~ .column,
 .about__section.has-4-columns .is-section-header ~ .column,
 .about__section.has-overlap-style .is-section-header ~ .column {
-	-ms-grid-row: 2;
 	grid-row-start: 2;
 }
 
 .about__section.has-overlap-style {
-	-ms-grid-columns: (1fr)[7];
 	grid-template-columns: repeat(7, 1fr);
 }
 
 .about__section.has-overlap-style .column {
-	-ms-grid-row: 1;
 	grid-row-start: 1;
 }
 
 .about__section.has-overlap-style .column:nth-of-type(2n+1) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 	-ms-grid-column-span: 3;
 	grid-column-end: span 3;
 }
 
 .about__section.has-overlap-style .column:nth-of-type(2n) {
-	-ms-grid-column: 4;
 	grid-column-start: 4;
 	-ms-grid-column-span: 3;
 	grid-column-end: span 3;
@@ -380,23 +354,19 @@
 	}
 
 	.about__section.has-4-columns {
-		-ms-grid-columns: (1fr)[2];
 		grid-template-columns: repeat(2, 1fr);
 	}
 
 	.about__section.has-4-columns .column:nth-of-type(2n+1) {
-		-ms-grid-column: 1;
 		grid-column-start: 1;
 	}
 
 	.about__section.has-4-columns .column:nth-of-type(2n) {
-		-ms-grid-column: 2;
 		grid-column-start: 2;
 	}
 
 	.about__section.has-4-columns .column:nth-of-type(4n+3),
 	.about__section.has-4-columns .column:nth-of-type(4n) {
-		-ms-grid-row: 2;
 		grid-row-start: 2;
 	}
 
@@ -407,22 +377,18 @@
 
 	.about__section.has-4-columns .is-section-header ~ .column:nth-of-type(4n+3),
 	.about__section.has-4-columns .is-section-header ~ .column:nth-of-type(4n) {
-		-ms-grid-row: 3;
 		grid-row-start: 3;
 	}
 
 	.about__section.has-overlap-style {
-		-ms-grid-columns: 1fr;
 		grid-template-columns: 1fr;
 	}
 
 	/* At this size, the two columns fully overlap */
 	.about__section.has-overlap-style .column.column {
-		-ms-grid-column: 1;
 		grid-column-start: 1;
 		-ms-grid-column-span: 1;
 		grid-column-end: 2;
-		-ms-grid-row: 1;
 		grid-row-start: 1;
 		-ms-grid-row-span: 1;
 		grid-row-end: 2;
@@ -574,7 +540,6 @@
 
 .about__container .about__image-comparison img {
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 	width: auto;
 	max-width: none;
@@ -1048,7 +1013,6 @@
 .about-wrap .has-2-columns,
 .about-wrap .has-3-columns,
 .about-wrap .has-4-columns {
-	display: -ms-grid;
 	display: grid;
 	max-width: 800px;
 	margin-top: 40px;
@@ -1076,72 +1040,58 @@
 }
 
 .about-wrap .has-2-columns {
-	-ms-grid-columns: 1fr 1fr;
 	grid-template-columns: 1fr 1fr;
 }
 
 .about-wrap .has-2-columns .column:nth-of-type(2n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about-wrap .has-2-columns .column:nth-of-type(2n) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about-wrap .has-2-columns.is-wider-right {
-	-ms-grid-columns: 1fr 2fr;
 	grid-template-columns: 1fr 2fr;
 }
 
 .about-wrap .has-2-columns.is-wider-left {
-	-ms-grid-columns: 2fr 1fr;
 	grid-template-columns: 2fr 1fr;
 }
 
 .about-wrap .has-3-columns {
-	-ms-grid-columns: (1fr)[3];
 	grid-template-columns: repeat(3, 1fr);
 }
 
 .about-wrap .has-3-columns .column:nth-of-type(3n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about-wrap .has-3-columns .column:nth-of-type(3n+2) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about-wrap .has-3-columns .column:nth-of-type(3n) {
-	-ms-grid-column: 3;
 	grid-column-start: 3;
 }
 
 .about-wrap .has-4-columns {
-	-ms-grid-columns: (1fr)[4];
 	grid-template-columns: repeat(4, 1fr);
 }
 
 .about-wrap .has-4-columns .column:nth-of-type(4n+1) {
-	-ms-grid-column: 1;
 	grid-column-start: 1;
 }
 
 .about-wrap .has-4-columns .column:nth-of-type(4n+2) {
-	-ms-grid-column: 2;
 	grid-column-start: 2;
 }
 
 .about-wrap .has-4-columns .column:nth-of-type(4n+3) {
-	-ms-grid-column: 3;
 	grid-column-start: 3;
 }
 
 .about-wrap .has-4-columns .column:nth-of-type(4n) {
-	-ms-grid-column: 4;
 	grid-column-start: 4;
 }
 
@@ -1164,17 +1114,14 @@
 }
 
 .about-wrap .is-vertically-aligned-top {
-	-ms-grid-row-align: start;
 	align-self: start;
 }
 
 .about-wrap .is-vertically-aligned-center {
-	-ms-grid-row-align: center;
 	align-self: center;
 }
 
 .about-wrap .is-vertically-aligned-bottom {
-	-ms-grid-row-align: end;
 	align-self: end;
 }
 
@@ -1359,38 +1306,29 @@
 @media screen and (max-width: 782px) {
 	.about-wrap .has-3-columns,
 	.about-wrap .has-4-columns {
-		-ms-grid-columns: 1fr 1fr;
 		grid-template-columns: 1fr 1fr;
 	}
 
 	.about-wrap .has-3-columns .column:nth-of-type(3n+1),
 	.about-wrap .has-4-columns .column:nth-of-type(4n+1) {
-		-ms-grid-column: 1;
 		grid-column-start: 1;
-		-ms-grid-row: 1;
 		grid-row-start: 1;
 	}
 
 	.about-wrap .has-3-columns .column:nth-of-type(3n+2),
 	.about-wrap .has-4-columns .column:nth-of-type(4n+2) {
-		-ms-grid-column: 2;
 		grid-column-start: 2;
-		-ms-grid-row: 1;
 		grid-row-start: 1;
 	}
 
 	.about-wrap .has-3-columns .column:nth-of-type(3n),
 	.about-wrap .has-4-columns .column:nth-of-type(4n+3) {
-		-ms-grid-column: 1;
 		grid-column-start: 1;
-		-ms-grid-row: 2;
 		grid-row-start: 2;
 	}
 
 	.about-wrap .has-4-columns .column:nth-of-type(4n) {
-		-ms-grid-column: 2;
 		grid-column-start: 2;
-		-ms-grid-row: 2;
 		grid-row-start: 2;
 	}
 }
@@ -1409,7 +1347,6 @@
 
 	.about-wrap .has-2-columns.is-wider-right,
 	.about-wrap .has-2-columns.is-wider-left {
-		display: -ms-grid;
 		display: grid;
 	}
 }
diff --git a/src/wp-admin/css/admin-menu.css b/src/wp-admin/css/admin-menu.css
index e299fc3b46..801d518a85 100644
--- a/src/wp-admin/css/admin-menu.css
+++ b/src/wp-admin/css/admin-menu.css
@@ -155,7 +155,6 @@
 /* side admin menu */
 #adminmenu * {
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -357,7 +356,6 @@
 	word-wrap: break-word;
 	-ms-word-break: break-all;
 	word-break: break-word;
-	-ms-hyphens: auto;
 	-webkit-hyphens: auto;
 	hyphens: auto;
 }
diff --git a/src/wp-admin/css/common.css b/src/wp-admin/css/common.css
index 8130292a2c..0f27cc2a2a 100644
--- a/src/wp-admin/css/common.css
+++ b/src/wp-admin/css/common.css
@@ -2128,7 +2128,6 @@ html.wp-toolbar {
 .postbox .hndle,
 .stuffbox .hndle {
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -3520,7 +3519,6 @@ img {
 	border-left: 1px solid #dcdcde;
 	border-right: 1px solid #dcdcde;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -3752,10 +3750,6 @@ img {
 
 }
 
-@-ms-viewport {
-	width: device-width;
-}
-
 @media screen and (max-width: 782px) {
 	html.wp-toolbar {
 		padding-top: 46px;
diff --git a/src/wp-admin/css/customize-controls.css b/src/wp-admin/css/customize-controls.css
index acec17262d..3c687eb617 100644
--- a/src/wp-admin/css/customize-controls.css
+++ b/src/wp-admin/css/customize-controls.css
@@ -1265,7 +1265,6 @@ p.customize-section-description {
 	padding: 4px 5px;
 	border: 2px solid #f0f0f1;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -2388,7 +2387,6 @@ body.cheatin p {
 	margin: 0 0 0 10px;
 	transition: all 0.2s;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 	outline: none;
 }
diff --git a/src/wp-admin/css/customize-nav-menus.css b/src/wp-admin/css/customize-nav-menus.css
index 730fc7417b..0fa7bc4f15 100644
--- a/src/wp-admin/css/customize-nav-menus.css
+++ b/src/wp-admin/css/customize-nav-menus.css
@@ -512,7 +512,6 @@
 	transition: background-color 0.15s;
 	/* Reset the value inherited from the base .accordion-section-title style. Ticket #37589. */
 	-webkit-user-select: auto;
-	-ms-user-select: auto;
 	user-select: auto;
 }
 
diff --git a/src/wp-admin/css/customize-widgets.css b/src/wp-admin/css/customize-widgets.css
index 3e48c47800..52d9552be0 100644
--- a/src/wp-admin/css/customize-widgets.css
+++ b/src/wp-admin/css/customize-widgets.css
@@ -54,7 +54,6 @@
 	opacity: 0.7;
 	pointer-events: none;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -166,7 +165,6 @@
 	border-top: 1px solid #c3c4c7;
 	cursor: pointer;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
diff --git a/src/wp-admin/css/list-tables.css b/src/wp-admin/css/list-tables.css
index ddf7891ae2..2006bded2b 100644
--- a/src/wp-admin/css/list-tables.css
+++ b/src/wp-admin/css/list-tables.css
@@ -318,7 +318,6 @@ table.fixed {
 .fixed .column-role,
 .fixed .column-posts {
 	-webkit-hyphens: auto;
-	-ms-hyphens: auto;
 	hyphens: auto;
 }
 
@@ -1874,9 +1873,7 @@ div.action-links,
 
 	/* Make row actions more easy to select on mobile */
 	body:not(.plugins-php) .row-actions {
-		display: -ms-grid;
 		display: grid;
-		-ms-grid-columns: auto auto auto;
 		grid-template-columns: auto auto auto;
 		color: transparent;
 	}
@@ -2147,7 +2144,6 @@ div.action-links,
 
 	/* Drop row actions to two columns on a small screen */
 	.row-actions:not(.plugins-php) {
-		-ms-grid-columns: auto auto;
 		grid-template-columns: auto auto;
 	}
 
diff --git a/src/wp-admin/css/login.css b/src/wp-admin/css/login.css
index 2212624e95..5c4993c9bf 100644
--- a/src/wp-admin/css/login.css
+++ b/src/wp-admin/css/login.css
@@ -404,10 +404,6 @@ input::-ms-reveal {
 	display: none;
 }
 
-@-ms-viewport {
-	width: device-width;
-}
-
 @media screen and (max-height: 550px) {
 	#login {
 		padding: 20px 0;
diff --git a/src/wp-admin/css/site-health.css b/src/wp-admin/css/site-health.css
index 516142c421..7a67525a85 100644
--- a/src/wp-admin/css/site-health.css
+++ b/src/wp-admin/css/site-health.css
@@ -349,7 +349,6 @@
 	align-items: center;
 	justify-content: space-between;
 	-webkit-user-select: auto;
-	-ms-user-select: auto;
 	user-select: auto;
 }
 
diff --git a/src/wp-admin/css/themes.css b/src/wp-admin/css/themes.css
index 72ca1db0ee..950768d246 100644
--- a/src/wp-admin/css/themes.css
+++ b/src/wp-admin/css/themes.css
@@ -646,7 +646,6 @@ body.folded .theme-browser ~ .theme-overlay .theme-wrap {
 	border-radius: 2px;
 	margin: 0 0 -10px;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
diff --git a/src/wp-admin/css/widgets.css b/src/wp-admin/css/widgets.css
index 1703cef7cf..c5798c7fb1 100644
--- a/src/wp-admin/css/widgets.css
+++ b/src/wp-admin/css/widgets.css
@@ -37,7 +37,6 @@
 	white-space: nowrap;
 	text-overflow: ellipsis;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -423,7 +422,6 @@ div#widgets-left .widget-holder {
 	word-wrap: break-word;
 	-ms-word-break: break-all;
 	word-break: break-word;
-	-ms-hyphens: auto;
 	-webkit-hyphens: auto;
 	hyphens: auto;
 }
@@ -566,7 +564,6 @@ div#widgets-right .closed .widgets-sortables {
 .widgets-holder-wrap .sidebar-name,
 .widgets-holder-wrap .sidebar-description {
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
diff --git a/src/wp-includes/css/editor.css b/src/wp-includes/css/editor.css
index a5c8deee37..e75e9b7b4d 100644
--- a/src/wp-includes/css/editor.css
+++ b/src/wp-includes/css/editor.css
@@ -258,7 +258,6 @@ div.mce-inline-toolbar-grp {
 	margin-bottom: 8px;
 	position: absolute;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 	max-width: 98%;
 	z-index: 100100; /* Same as the other TinyMCE "panels" */
diff --git a/src/wp-includes/css/media-views.css b/src/wp-includes/css/media-views.css
index 4c03d88d56..efb19a16b2 100644
--- a/src/wp-includes/css/media-views.css
+++ b/src/wp-includes/css/media-views.css
@@ -609,7 +609,6 @@
 	border-right-style: solid;
 	border-right-color: #c3c4c7;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 }
 
@@ -948,7 +947,6 @@
 	list-style: none;
 	text-align: center;
 	-webkit-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
 	width: 25%;
 	box-sizing: border-box;