angular.js:13920 Error: [ng:areq] Argument 'Controller' is not a function, got undefined

There can be plenty of reason like
1- There is any bug or error in Controller JS code.

2- check if a controller with given name is registered via $controllerProvider

3- check if evaluating the string on the current scope returns a constructor

4- if $controllerProvider#allowGlobals, check window[constructor] on the global window object (not recommended)

5- Do Make sure to put the appname in ng-app directive on your angular root element (eg:- html) as well. Example:- ng-app="myApp"

6- If everything is fine and you are still getting the issue do remember to make sure you have the right file included in the scripts.

7-You have not defined the same module twice in different places which results in any entities defined previously on the same module to be cleared out, Example angular.module('app',[]).controller(.. and again in another place angular.module('app',[]).service(.. (with both the scripts included of course) can cause the previously registered controller on the module app to be cleared out with the second recreation of module.

8- Re-declaration

var webApp = angular.module('webApp', [...]); webApp.controller('Controller', ...);
var webApp = angular.module('webApp', [...]);
webApp.controller('Controller1', ...);