diff --git a/src/vs/editor/browser/widget/codeEditorWidget.ts b/src/vs/editor/browser/widget/codeEditorWidget.ts
index e571b75dd3b..c3be18fe35d 100644
--- a/src/vs/editor/browser/widget/codeEditorWidget.ts
+++ b/src/vs/editor/browser/widget/codeEditorWidget.ts
@@ -1848,4 +1848,6 @@ registerThemingParticipant((theme, collector) => {
 	if (unnecessaryBorder) {
 		collector.addRule(`.${SHOW_UNUSED_ENABLED_CLASS} .monaco-editor .${ClassName.EditorUnnecessaryDecoration} { border-bottom: 2px dashed ${unnecessaryBorder}; }`);
 	}
+
+	collector.addRule(`.monaco-editor .${ClassName.EditorDeprecatedInlineDecoration} { text-decoration: line-through; }`);
 });
diff --git a/src/vs/editor/common/model/intervalTree.ts b/src/vs/editor/common/model/intervalTree.ts
index 496e77b9ef4..d400024e7c5 100644
--- a/src/vs/editor/common/model/intervalTree.ts
+++ b/src/vs/editor/common/model/intervalTree.ts
@@ -17,7 +17,8 @@ export const enum ClassName {
 	EditorWarningDecoration = 'squiggly-warning',
 	EditorErrorDecoration = 'squiggly-error',
 	EditorUnnecessaryDecoration = 'squiggly-unnecessary',
-	EditorUnnecessaryInlineDecoration = 'squiggly-inline-unnecessary'
+	EditorUnnecessaryInlineDecoration = 'squiggly-inline-unnecessary',
+	EditorDeprecatedInlineDecoration = 'squiggly-inline-deprecated'
 }
 
 export const enum NodeColor {
diff --git a/src/vs/editor/common/services/markerDecorationsServiceImpl.ts b/src/vs/editor/common/services/markerDecorationsServiceImpl.ts
index a319e8004b6..3da62fed16f 100644
--- a/src/vs/editor/common/services/markerDecorationsServiceImpl.ts
+++ b/src/vs/editor/common/services/markerDecorationsServiceImpl.ts
@@ -221,6 +221,9 @@ export class MarkerDecorationsService extends Disposable implements IMarkerDecor
 			if (marker.tags.indexOf(MarkerTag.Unnecessary) !== -1) {
 				inlineClassName = ClassName.EditorUnnecessaryInlineDecoration;
 			}
+			if (marker.tags.indexOf(MarkerTag.Deprecated) !== -1) {
+				inlineClassName = ClassName.EditorDeprecatedInlineDecoration;
+			}
 		}
 
 		return {
diff --git a/src/vs/editor/common/standalone/standaloneEnums.ts b/src/vs/editor/common/standalone/standaloneEnums.ts
index df80861b2a8..46d295d2398 100644
--- a/src/vs/editor/common/standalone/standaloneEnums.ts
+++ b/src/vs/editor/common/standalone/standaloneEnums.ts
@@ -7,7 +7,8 @@
 
 
 export enum MarkerTag {
-	Unnecessary = 1
+	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum MarkerSeverity {
diff --git a/src/vs/monaco.d.ts b/src/vs/monaco.d.ts
index e08ad368312..eb2000206ce 100644
--- a/src/vs/monaco.d.ts
+++ b/src/vs/monaco.d.ts
@@ -29,7 +29,8 @@ declare namespace monaco {
 
 
 	export enum MarkerTag {
-		Unnecessary = 1
+		Unnecessary = 1,
+		Deprecated = 2
 	}
 
 	export enum MarkerSeverity {
diff --git a/src/vs/platform/markers/common/markers.ts b/src/vs/platform/markers/common/markers.ts
index 9461b506c21..235c4b12f36 100644
--- a/src/vs/platform/markers/common/markers.ts
+++ b/src/vs/platform/markers/common/markers.ts
@@ -39,6 +39,7 @@ export interface IRelatedInformation {
 
 export const enum MarkerTag {
 	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum MarkerSeverity {
diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index 430967c999e..d410fcedffd 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1290,4 +1290,18 @@ declare module 'vscode' {
 	}
 
 	//#endregion
+
+	//#region Deprecated support
+
+	export enum DiagnosticTag {
+		/**
+		 * Deprecated or obsolete code
+		 *
+		 * Can be used to style with strikeout or other "obsolete" styling. See:
+		 * https://github.com/microsoft/vscode/issues/50972
+		 */
+		Deprecated = 2,
+	}
+
+	//#endregion
 }
diff --git a/src/vs/workbench/api/common/extHostTypeConverters.ts b/src/vs/workbench/api/common/extHostTypeConverters.ts
index de31343f036..39b2cda9188 100644
--- a/src/vs/workbench/api/common/extHostTypeConverters.ts
+++ b/src/vs/workbench/api/common/extHostTypeConverters.ts
@@ -108,6 +108,8 @@ export namespace DiagnosticTag {
 		switch (value) {
 			case types.DiagnosticTag.Unnecessary:
 				return MarkerTag.Unnecessary;
+			case types.DiagnosticTag.Deprecated:
+				return MarkerTag.Deprecated;
 		}
 		return undefined;
 	}
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index b8aebf92b45..de8d3eec8b3 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -773,6 +773,7 @@ export class SnippetString {
 
 export enum DiagnosticTag {
 	Unnecessary = 1,
+	Deprecated = 2
 }
 
 export enum DiagnosticSeverity {