diff --git a/packages/aws-cdk-lib/aws-lambda/lib/runtime.ts b/packages/aws-cdk-lib/aws-lambda/lib/runtime.ts
index b292df2d47106..0ef969b168669 100644
--- a/packages/aws-cdk-lib/aws-lambda/lib/runtime.ts
+++ b/packages/aws-cdk-lib/aws-lambda/lib/runtime.ts
@@ -252,6 +252,13 @@ export class Runtime {
     supportsSnapStart: true,
   });
 
+  /**
+   * The .NET 9 runtime (dotnet9)
+   */
+  public static readonly DOTNET_9 = new Runtime('dotnet9', RuntimeFamily.DOTNET_CORE, {
+    supportsSnapStart: true,
+  });
+
   /**
    * The .NET Core 1.0 runtime (dotnetcore1.0)
    * @deprecated Legacy runtime no longer supported by AWS Lambda. Migrate to the latest .NET Core runtime.