diff --git a/.gitignore b/.gitignore
index 68b162ad..8de59eaf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ npm-debug.log
 *.perspectivev3
 *.xcuserstate
 project.xcworkspace/
+atlassian-ide-plugin
 xcuserdata/
 
 # Example
diff --git a/android/src/main/java/io/invertase/firebase/auth/RNFirebaseAuth.java b/android/src/main/java/io/invertase/firebase/auth/RNFirebaseAuth.java
index 6524f349..0679b322 100644
--- a/android/src/main/java/io/invertase/firebase/auth/RNFirebaseAuth.java
+++ b/android/src/main/java/io/invertase/firebase/auth/RNFirebaseAuth.java
@@ -6,6 +6,7 @@ import android.util.Log;
 import android.net.Uri;
 import android.support.annotation.NonNull;
 
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.HashMap;
 import java.util.List;
@@ -1123,6 +1124,7 @@ class RNFirebaseAuth extends ReactContextBaseJavaModule {
   /**
    * fetchProvidersForEmail
    *
+   * @param appName
    * @param promise
    */
   @ReactMethod
@@ -1157,6 +1159,31 @@ class RNFirebaseAuth extends ReactContextBaseJavaModule {
       });
   }
 
+  /**
+   * Set the language code for the auth module
+   * @param appName
+   * @param code
+   */
+  @ReactMethod
+  public void setLanguageCode(String appName, String code) {
+    FirebaseApp firebaseApp = FirebaseApp.getInstance(appName);
+    FirebaseAuth firebaseAuth = FirebaseAuth.getInstance(firebaseApp);
+
+    firebaseAuth.setLanguageCode(code);
+  }
+
+  /**
+   * Use the device language
+   * @param appName
+   */
+  @ReactMethod
+  public void useDeviceLanguage(String appName) {
+    FirebaseApp firebaseApp = FirebaseApp.getInstance(appName);
+    FirebaseAuth firebaseAuth = FirebaseAuth.getInstance(firebaseApp);
+
+    firebaseAuth.useAppLanguage();
+  }
+
   /* ------------------
    * INTERNAL HELPERS
    * ---------------- */
@@ -1431,4 +1458,29 @@ class RNFirebaseAuth extends ReactContextBaseJavaModule {
     eventMap.putMap("state", state);
     Utils.sendEvent(mReactContext, "phone_auth_state_changed", eventMap);
   }
+
+  /**
+   * Constants bootstrapped on react native app boot
+   *
+   * @return
+   */
+  @Override
+  public Map<String, Object> getConstants() {
+    Map<String, Object> constants = new HashMap<>();
+
+    List<FirebaseApp> firebaseAppList = FirebaseApp.getApps(getReactApplicationContext());
+    final Map<String, Object> appLanguage = new HashMap<>();
+
+    for (FirebaseApp app : firebaseAppList) {
+      String appName = app.getName();
+
+      FirebaseApp instance = FirebaseApp.getInstance(appName);
+      FirebaseAuth firebaseAuth = FirebaseAuth.getInstance(instance);
+
+      appLanguage.put(appName, firebaseAuth.getLanguageCode());
+    }
+
+    constants.put("APP_LANGUAGE", appLanguage);
+    return constants;
+  }
 }
diff --git a/ios/RNFirebase/auth/RNFirebaseAuth.m b/ios/RNFirebase/auth/RNFirebaseAuth.m
index 8d87f9d5..550417fe 100644
--- a/ios/RNFirebase/auth/RNFirebaseAuth.m
+++ b/ios/RNFirebase/auth/RNFirebaseAuth.m
@@ -902,6 +902,34 @@ RCT_EXPORT_METHOD(fetchProvidersForEmail:
     return credential;
 }
 
+/**
+ setLanguageCode
+
+ @param NSString code
+ @return
+ */
+RCT_EXPORT_METHOD(setLanguageCode:
+    (NSString *) appDisplayName
+            code:
+            (NSString *) code) {
+    FIRApp *firApp = [RNFirebaseUtil getApp:appDisplayName];
+
+    [FIRAuth authWithApp:firApp].languageCode = code;
+}
+
+/**
+ useDeviceLanguage
+
+ @param NSString code
+ @return
+ */
+RCT_EXPORT_METHOD(useDeviceLanguage:
+    (NSString *) appDisplayName) {
+    FIRApp *firApp = [RNFirebaseUtil getApp:appDisplayName];
+
+     [[FIRAuth authWithApp:firApp] useAppLanguage];
+}
+
 // This is here to protect against bugs in the iOS SDK which don't
 // correctly refresh the user object when performing certain operations
 - (void)reloadAndReturnUser:(FIRUser *)user
@@ -1128,6 +1156,25 @@ RCT_EXPORT_METHOD(fetchProvidersForEmail:
     return output;
 }
 
+/**
+ * React native constant exports - exports native firebase apps mainly
+ * @return NSDictionary
+ */
+- (NSDictionary *)constantsToExport {
+    NSMutableDictionary *constants = [NSMutableDictionary new];
+    NSDictionary *firApps = [FIRApp allApps];
+    NSMutableDictionary *appLanguage = [NSMutableDictionary new];
+
+    for (id key in firApps) {
+        FIRApp *firApp = firApps[key];
+
+        appLanguage[firApp.name] = [FIRAuth authWithApp:firApp].languageCode;
+    }
+
+    constants[@"APP_LANGUAGE"] = appLanguage;
+    return constants;
+}
+
 /**
  Converts a FIRUser instance into a dictionary to send via RNBridge
 
diff --git a/lib/index.d.ts b/lib/index.d.ts
index 204900da..628a806f 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -649,6 +649,11 @@ declare module "react-native-firebase" {
          */
         currentUser: User | null
 
+        /**
+         * Gets/Sets the language for the app instance
+         */
+        languageCode: string | null;
+
         /**
          * Listen for changes in the users auth state (logging in and out).
          * This method returns a unsubscribe function to stop listening to events.
diff --git a/lib/modules/auth/index.js b/lib/modules/auth/index.js
index 75a64f19..ebdc05cc 100644
--- a/lib/modules/auth/index.js
+++ b/lib/modules/auth/index.js
@@ -49,6 +49,7 @@ export default class Auth extends ModuleBase {
     });
     this._user = null;
     this._authResult = null;
+    this._languageCode = getNativeModule(this).APP_LANGUAGE[app._name] || getNativeModule(this).APP_LANGUAGE['[DEFAULT]'];
 
     SharedEventEmitter.addListener(
       // sub to internal native event - this fans out to
@@ -327,6 +328,16 @@ export default class Auth extends ModuleBase {
     return getNativeModule(this).fetchProvidersForEmail(email);
   }
 
+  /**
+   * Sets the language for the auth module
+   * @param code
+   * @returns {*}
+   */
+  set languageCode(code: string) {
+    this._languageCode = code;
+    getNativeModule(this).setLanguageCode(code);
+  }
+
   /**
    * Get the currently signed in user
    * @return {Promise}
@@ -335,6 +346,10 @@ export default class Auth extends ModuleBase {
     return this._user;
   }
 
+  get languageCode(): string {
+    return this._languageCode;
+  }
+
   /**
    * KNOWN UNSUPPORTED METHODS
    */
@@ -358,6 +373,11 @@ export default class Auth extends ModuleBase {
   signInWithRedirect() {
     throw new Error(INTERNALS.STRINGS.ERROR_UNSUPPORTED_MODULE_METHOD('auth', 'signInWithRedirect'));
   }
+
+  // firebase issue - https://github.com/invertase/react-native-firebase/pull/655#issuecomment-349904680
+  useDeviceLanguage() {
+    throw new Error(INTERNALS.STRINGS.ERROR_UNSUPPORTED_MODULE_METHOD('auth', 'useDeviceLanguage'));
+  }
 }
 
 export const statics = {
diff --git a/tests/src/tests/auth/authTests.js b/tests/src/tests/auth/authTests.js
index ad838968..5848db26 100644
--- a/tests/src/tests/auth/authTests.js
+++ b/tests/src/tests/auth/authTests.js
@@ -356,6 +356,18 @@ function authTests({ tryCatch, describe, it, firebase }) {
         return firebase.native.auth().signOut().then(successCb).catch(failureCb);
       });
     });
+
+    it('it should change the language code', () => {
+      firebase.native.auth().languageCode = 'en';
+      if (firebase.native.auth().languageCode !== 'en') {
+        throw new Error('Expected language code to be "en".');
+      }
+      firebase.native.auth().languageCode = 'fr';
+      if (firebase.native.auth().languageCode !== 'fr') {
+        throw new Error('Expected language code to be "fr".');
+      }
+      firebase.native.auth().languageCode = 'en';
+    });
   });
 }