diff --git a/src/aad.url.builder.spec.ts b/src/aad.url.builder.spec.ts
index 7c07ecb..da0957e 100644
--- a/src/aad.url.builder.spec.ts
+++ b/src/aad.url.builder.spec.ts
@@ -52,6 +52,16 @@ describe('AadUrlBuilder', () => {
         actualUrl = actualUrl.replace(expectedNonce, '');
     });
 
+    it('should allow using custom login url', () => {
+        let options = createConfig();
+        options.loginUrl = 'https://my.custom.ad/';
+        let expectedLocation = options.loginUrl + options.tenant + '/oauth2/authorize';
+
+        let actualUrl = new AadUrlBuilder(new GuidGenerator()).with(<AadUrlConfig>options).build();
+
+        expect(_.startsWith(actualUrl, expectedLocation)).toBe(true, 'incorrect location');
+    });
+
     function createConfig(): AadUrlConfig {
         return {
             nonce: new GuidGenerator().generate(),
diff --git a/src/aad.url.builder.ts b/src/aad.url.builder.ts
index 3281485..97184f4 100644
--- a/src/aad.url.builder.ts
+++ b/src/aad.url.builder.ts
@@ -13,8 +13,8 @@ export class AadUrlBuilder {
     private clientRequestId: string;
     private libVersion: string;
     private extraQueryParameter: string;
+    private loginUrl: string;
     private guidGenerator: GuidGenerator;
-    public static MicrosoftLoginUrl: string = 'https://login.microsoftonline.com/';
 
     constructor(guidGenerator: GuidGenerator) {
         this.guidGenerator = guidGenerator;
@@ -23,6 +23,7 @@ export class AadUrlBuilder {
         this.clientRequestId = this.guidGenerator.generate();
         this.responseType = 'id_token';
         this.libVersion = '1.0.0';
+        this.loginUrl = 'https://login.microsoftonline.com/';
         this.redirectUri = window.location.href;
     }
 
@@ -38,12 +39,13 @@ export class AadUrlBuilder {
         this.clientRequestId = options.clientRequestId || this.clientRequestId;
         this.libVersion = options.libVersion || this.libVersion;
         this.extraQueryParameter = options.extraQueryParameter || this.extraQueryParameter;
+        this.loginUrl = options.loginUrl || this.loginUrl;
         return this;
     }
 
     public build() {
 
-        var urlNavigate = AadUrlBuilder.MicrosoftLoginUrl + this.tenant + '/oauth2/authorize';
+        var urlNavigate = this.loginUrl + this.tenant + '/oauth2/authorize';
         urlNavigate = urlNavigate + this.serialize() + this.addLibMetadata();
         urlNavigate = urlNavigate + '&nonce=' + encodeURIComponent(this.nonce);
         return urlNavigate;
diff --git a/src/aad.url.config.ts b/src/aad.url.config.ts
index baac3e9..9816e32 100644
--- a/src/aad.url.config.ts
+++ b/src/aad.url.config.ts
@@ -10,4 +10,5 @@ export interface AadUrlConfig {
     clientRequestId?: string;
     libVersion?: string;
     extraQueryParameter?: string;
+    loginUrl?: string;
 }
\ No newline at end of file
diff --git a/src/adal.config.ts b/src/adal.config.ts
index b25ad19..546cedf 100644
--- a/src/adal.config.ts
+++ b/src/adal.config.ts
@@ -5,6 +5,7 @@ export class AdalConfig {
         public redirectUri: string,
         public postLogoutRedirectUrl?: string,
         public responseType?: string,
-        public extraQueryParameter?: string) {
+        public extraQueryParameter?: string,
+        public loginUrl?: string) {
     };
 }
\ No newline at end of file