3 files changed, 9 insertions, 0 deletions
diff --git a/cli/js/lib.deno.unstable.d.ts b/cli/js/lib.deno.unstable.d.ts
index aebd7f964..dc50416fc 100644
--- a/cli/js/lib.deno.unstable.d.ts
+++ b/cli/js/lib.deno.unstable.d.ts
@@ -1245,4 +1245,7 @@ declare namespace Deno {
    *  Requires `allow-env` permission.
    */
   export function hostname(): string;
+
+  /** **UNSTABLE**: The URL of the file that was originally executed from the command-line. */
+  export const mainModule: string;
 }
diff --git a/cli/js/ops/runtime.ts b/cli/js/ops/runtime.ts
index 632424327..70addf469 100644
--- a/cli/js/ops/runtime.ts
+++ b/cli/js/ops/runtime.ts
@@ -21,6 +21,10 @@ export function opStart(): Start {
   return sendSync("op_start");
 }
 
+export function opMainModule(): string {
+  return sendSync("op_main_module");
+}
+
 export interface Metrics {
   opsDispatched: number;
   opsDispatchedSync: number;
diff --git a/cli/js/runtime_main.ts b/cli/js/runtime_main.ts
index 58405f673..25a6b0f93 100644
--- a/cli/js/runtime_main.ts
+++ b/cli/js/runtime_main.ts
@@ -9,6 +9,7 @@
 
 import * as denoNs from "./deno.ts";
 import * as denoUnstableNs from "./deno_unstable.ts";
+import { opMainModule } from "./ops/runtime.ts";
 import { exit } from "./ops/os.ts";
 import {
   readOnly,
@@ -106,6 +107,7 @@ export function bootstrapMainRuntime(): void {
   if (unstableFlag) {
     Object.defineProperties(globalThis, unstableMethods);
     Object.defineProperties(globalThis, unstableProperties);
+    Object.defineProperty(denoNs, "mainModule", getterOnly(opMainModule));
     Object.assign(denoNs, denoUnstableNs);
   }