diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1fa54a24e354..bbc251ee0e241 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@
 
 - [plugin] Avoid pollution of all toolbars by actions contributed by tree views in extensions [#13768](https://github.com/eclipse-theia/theia/pull/13768) - contributed on behalf of STMicroelectronics
 
+- [debug] stub activeStackItem and related change event in debug namespace [#13847](https://github.com/eclipse-theia/theia/pull/13847) - contributed on behalf of STMicroelectronics
+
 <a name="breaking_changes_not_yet_released">[Breaking Changes:](#breaking_changes_not_yet_released)</a> 
 
 - [filesystem] Adjusted the "Save As" mechanism. It now assumes that `Saveable.getSnapshot()` returns a full snapshot of the editor model [#13689](https://github.com/eclipse-theia/theia/pull/13689). 
diff --git a/packages/plugin-ext/src/plugin/plugin-context.ts b/packages/plugin-ext/src/plugin/plugin-context.ts
index 4aa0d22c6cb15..c37330cbf90de 100644
--- a/packages/plugin-ext/src/plugin/plugin-context.ts
+++ b/packages/plugin-ext/src/plugin/plugin-context.ts
@@ -124,6 +124,8 @@ import {
     Breakpoint,
     SourceBreakpoint,
     FunctionBreakpoint,
+    DebugStackFrame,
+    DebugThread,
     FoldingRange,
     FoldingRangeKind,
     SelectionRange,
@@ -1090,6 +1092,14 @@ export function createAPIFactory(
             get onDidChangeBreakpoints(): theia.Event<theia.BreakpointsChangeEvent> {
                 return debugExt.onDidChangeBreakpoints;
             },
+            /** @stubbed */
+            get activeStackItem(): DebugThread | DebugStackFrame | undefined {
+                return undefined;
+            },
+            /** @stubbed */
+            get onDidChangeActiveStackItem(): theia.Event<DebugThread | DebugStackFrame | undefined> {
+                return Event.None;
+            },
             registerDebugAdapterDescriptorFactory(debugType: string, factory: theia.DebugAdapterDescriptorFactory): Disposable {
                 return debugExt.registerDebugAdapterDescriptorFactory(debugType, factory);
             },
@@ -1372,6 +1382,8 @@ export function createAPIFactory(
             Breakpoint,
             SourceBreakpoint,
             FunctionBreakpoint,
+            DebugStackFrame,
+            DebugThread,
             Color,
             ColorInformation,
             ColorPresentation,
diff --git a/packages/plugin-ext/src/plugin/types-impl.ts b/packages/plugin-ext/src/plugin/types-impl.ts
index 4209dd20d62d8..4e5bbd16133c3 100644
--- a/packages/plugin-ext/src/plugin/types-impl.ts
+++ b/packages/plugin-ext/src/plugin/types-impl.ts
@@ -3028,6 +3028,14 @@ export class FunctionBreakpoint extends Breakpoint {
     }
 }
 
+export class DebugThread {
+    private constructor(readonly session: theia.DebugSession, readonly threadId: number) { }
+}
+
+export class DebugStackFrame {
+      private constructor(readonly session: theia.DebugSession, readonly threadId: number, readonly frameId: number) { }
+}
+
 @es5ClassCompat
 export class Color {
     readonly red: number;
diff --git a/packages/plugin/src/theia.d.ts b/packages/plugin/src/theia.d.ts
index 07913feef680d..a3f00380cbe8b 100644
--- a/packages/plugin/src/theia.d.ts
+++ b/packages/plugin/src/theia.d.ts
@@ -12448,6 +12448,50 @@ export module '@theia/plugin' {
         Dynamic = 2
     }
 
+    /**
+     * Represents a thread in a debug session.
+     */
+    export class DebugThread {
+        /**
+         * Debug session for thread.
+         */
+        readonly session: DebugSession;
+
+        /**
+         * ID of the associated thread in the debug protocol.
+         */
+        readonly threadId: number;
+
+        /**
+         * @hidden
+         */
+        private constructor(session: DebugSession, threadId: number);
+    }
+
+    /**
+     * Represents a stack frame in a debug session.
+     */
+    export class DebugStackFrame {
+        /**
+         * Debug session for thread.
+         */
+        readonly session: DebugSession;
+
+        /**
+         * ID of the associated thread in the debug protocol.
+         */
+        readonly threadId: number;
+        /**
+         * ID of the stack frame in the debug protocol.
+         */
+        readonly frameId: number;
+
+        /**
+         * @hidden
+         */
+        private constructor(session: DebugSession, threadId: number, frameId: number);
+    }
+
     /**
      * Namespace for debug functionality.
      */
@@ -12497,6 +12541,21 @@ export module '@theia/plugin' {
          */
         export const onDidChangeBreakpoints: Event<BreakpointsChangeEvent>;
 
+        /**
+         * The currently focused thread or stack frame, or `undefined` if no
+         * thread or stack is focused. A thread can be focused any time there is
+         * an active debug session, while a stack frame can only be focused when
+         * a session is paused and the call stack has been retrieved.
+         * @stubbed
+         */
+        export const activeStackItem: DebugThread | DebugStackFrame | undefined;
+
+        /**
+         * An event which fires when the {@link debug.activeStackItem} has changed.
+         * @stubbed
+         */
+        export const onDidChangeActiveStackItem: Event<DebugThread | DebugStackFrame | undefined>;
+
         /**
          * Register a {@link DebugAdapterDescriptorFactory debug adapter descriptor factory} for a specific debug type.
          * An extension is only allowed to register a DebugAdapterDescriptorFactory for the debug type(s) defined by the extension. Otherwise an error is thrown.