diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 964ac084..2f6954ff 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -209,6 +209,9 @@ The User name space is accessible via `OneSignal.User` and provides access to us
 | **Flutter** | **Description** |
 | ----------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `OneSignal.User.setLanguage("en");` | *Set the 2-character language for this user.* |
+| `OneSignal.User.addObserver(OnUserChangeObserver observer);` <br><br>**_See below for usage_** | *Add a User State observer which contains the nullable onesignalId and externalId. The listener will be fired when these values change.* |
+| `await OneSignal.User.getOnesignalId();` | *Returns the nullable OneSignal ID for the current user.* |
+| `await OneSignal.User.getExternalId();` | *Returns the nullable External ID for the current user.* |
 | `OneSignal.User.addAlias("ALIAS_LABEL", "ALIAS_ID");` | *Set an alias for the current user. If this alias label already exists on this user, it will be overwritten with the new alias id.* |
 | `OneSignal.User.addAliases({ALIAS_LABEL_01: "ALIAS_ID_01", ALIAS_LABEL_02: "ALIAS_ID_02"});` | *Set aliases for the current user. If any alias already exists, it will be overwritten to the new values.* |
 | `OneSignal.User.removeAlias("ALIAS_LABEL");` | *Remove an alias from the current user.* |
@@ -223,6 +226,20 @@ The User name space is accessible via `OneSignal.User` and provides access to us
 | `OneSignal.User.removeTags(["KEY_01", "KEY_02"]);` | *Remove multiple tags with the provided keys from the current user.* |
 | `OneSignal.User.getTags();` | *Returns the local tags for the current user.* |
 
+### User State Observer
+
+The `OnUserChangeObserver` will be fired when the user changes. This method's parameter is the current `UserChangedState` which includes the current state.
+
+```dart
+OneSignal.User.addObserver((state) {
+	var userState = state.jsonRepresentation();
+    print('OneSignal user changed: $userState');
+});
+
+/// Remove a user state observer that has been previously added.
+OneSignal.User.removeObserver(observer);
+```
+
 
 ## Push Subscription Namespace
 
diff --git a/android/src/main/java/com/onesignal/flutter/OneSignalSerializer.java b/android/src/main/java/com/onesignal/flutter/OneSignalSerializer.java
index d486842e..69831527 100644
--- a/android/src/main/java/com/onesignal/flutter/OneSignalSerializer.java
+++ b/android/src/main/java/com/onesignal/flutter/OneSignalSerializer.java
@@ -2,6 +2,8 @@
 
 import android.util.Log;
 
+import com.onesignal.user.state.UserChangedState;
+import com.onesignal.user.state.UserState;
 import com.onesignal.user.subscriptions.ISubscription;
 import com.onesignal.user.subscriptions.IPushSubscription;
 import com.onesignal.user.subscriptions.PushSubscriptionChangedState;
@@ -187,6 +189,18 @@ static HashMap<String, Object> convertPushSubscriptionState(PushSubscriptionStat
         return hash;
     }
 
+    static HashMap<String, Object> convertUserState(UserState state) throws JSONException {
+        HashMap<String, Object> hash = new HashMap<>();
+    
+        String onesignalId = setNullIfEmpty(state.getOnesignalId());
+        String externalId = setNullIfEmpty(state.getExternalId());
+    
+        hash.put("onesignalId", onesignalId);
+        hash.put("externalId", externalId);
+    
+        return hash;
+    }
+
     static HashMap<String, Object> convertOnPushSubscriptionChange(PushSubscriptionChangedState changedState) throws JSONException {
         HashMap<String, Object> hash = new HashMap<>();
         
@@ -197,6 +211,14 @@ static HashMap<String, Object> convertOnPushSubscriptionChange(PushSubscriptionC
         return hash;
     }
 
+    static HashMap<String, Object> convertOnUserStateChange(UserChangedState changedState) throws JSONException {
+        HashMap<String, Object> hash = new HashMap<>();
+
+        
+        hash.put("current", convertUserState(changedState.getCurrent()));
+    
+        return hash;
+    }
 
     static HashMap<String, Object> convertJSONObjectToHashMap(JSONObject object) throws JSONException {
         HashMap<String, Object> hash = new HashMap<>();
@@ -242,4 +264,9 @@ else if (val instanceof JSONObject)
 
         return list;
     }
+
+    /** Helper method to return null value if string is empty **/
+    static String setNullIfEmpty(String value) {
+        return value.isEmpty() ? null : value;
+    }
 }
diff --git a/android/src/main/java/com/onesignal/flutter/OneSignalUser.java b/android/src/main/java/com/onesignal/flutter/OneSignalUser.java
index accd29cc..b14c0087 100644
--- a/android/src/main/java/com/onesignal/flutter/OneSignalUser.java
+++ b/android/src/main/java/com/onesignal/flutter/OneSignalUser.java
@@ -2,6 +2,9 @@
 
 import com.onesignal.OneSignal;
 import com.onesignal.debug.LogLevel;
+import com.onesignal.debug.internal.logging.Logging;
+import com.onesignal.user.state.IUserStateObserver;
+import com.onesignal.user.state.UserChangedState;
 
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -18,8 +21,7 @@
 import io.flutter.plugin.common.PluginRegistry;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
 
-public class OneSignalUser extends FlutterRegistrarResponder implements MethodCallHandler {
-    private MethodChannel channel;
+public class OneSignalUser extends FlutterRegistrarResponder implements MethodCallHandler, IUserStateObserver {
 
     static void registerWith(BinaryMessenger messenger) {
         OneSignalUser controller = new OneSignalUser();
@@ -32,6 +34,10 @@ static void registerWith(BinaryMessenger messenger) {
     public void onMethodCall(MethodCall call, Result result) {
         if (call.method.contentEquals("OneSignal#setLanguage"))
             this.setLanguage(call, result);
+        else if (call.method.contentEquals("OneSignal#getOnesignalId"))
+            this.getOnesignalId(call, result);
+        else if (call.method.contentEquals("OneSignal#getExternalId"))
+            this.getExternalId(call, result);
         else if (call.method.contentEquals("OneSignal#addAliases"))
             this.addAliases(call, result);
         else if (call.method.contentEquals("OneSignal#removeAliases"))
@@ -50,6 +56,8 @@ else if (call.method.contentEquals("OneSignal#removeTags"))
             this.removeTags(call, result);
         else if (call.method.contentEquals("OneSignal#getTags"))
             this.getTags(call, result);
+        else if (call.method.contentEquals("OneSignal#lifecycleInit"))
+            this.lifecycleInit();
         else
             replyNotImplemented(result);
     }
@@ -63,6 +71,26 @@ private void setLanguage(MethodCall call, Result result) {
         replySuccess(result, null);
     }
 
+    private void lifecycleInit() {
+        OneSignal.getUser().addObserver(this);
+    }
+
+    private void getOnesignalId(MethodCall call, Result result) {
+        String onesignalId = OneSignal.getUser().getOnesignalId();
+        if (onesignalId.isEmpty()) {
+            onesignalId = null;
+        }
+        replySuccess(result, onesignalId);
+    }      
+
+    private void getExternalId(MethodCall call, Result result) {
+        String externalId = OneSignal.getUser().getExternalId();
+        if (externalId.isEmpty()) {
+            externalId = null;
+        }
+        replySuccess(result, externalId);
+    }
+    
     private void addAliases(MethodCall call, Result result) {
         // call.arguments is being casted to a Map<String, Object> so a try-catch with
         //  a ClassCastException will be thrown
@@ -130,4 +158,14 @@ private void removeTags(MethodCall call, Result result) {
     private void getTags(MethodCall call, Result result) {
         replySuccess(result, OneSignal.getUser().getTags());
     }
+
+    @Override
+    public void onUserStateChange(UserChangedState userChangedState) {
+        try {
+            invokeMethodOnUiThread("OneSignal#onUserStateChange", OneSignalSerializer.convertOnUserStateChange(userChangedState));
+        } catch (JSONException e) {
+            e.getStackTrace();
+            Logging.error("Encountered an error attempting to convert UserChangedState object to hash map:" + e.toString(), null);
+        }
+    }
 }
diff --git a/example/lib/main.dart b/example/lib/main.dart
index 65cbb785..1016ad3d 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -53,6 +53,11 @@ class _MyAppState extends State<MyApp> {
       print(state.current.jsonRepresentation());
     });
 
+    OneSignal.User.addObserver((state) {
+      var userState = state.jsonRepresentation();
+      print('OneSignal user changed: $userState');
+    });
+
     OneSignal.Notifications.addPermissionObserver((state) {
       print("Has permission " + state.toString());
     });
@@ -193,6 +198,11 @@ class _MyAppState extends State<MyApp> {
     OneSignal.Location.setShared(true);
   }
 
+  void _handleGetExternalId() async {
+    var externalId = await OneSignal.User.getExternalId();
+    print('External ID: $externalId');
+  }
+
   void _handleLogin() {
     print("Setting external user ID");
     if (_externalUserId == null) return;
@@ -205,6 +215,11 @@ class _MyAppState extends State<MyApp> {
     OneSignal.User.removeAlias("fb_id");
   }
 
+  void _handleGetOnesignalId() async {
+    var onesignalId = await OneSignal.User.getOnesignalId();
+    print('OneSignal ID: $onesignalId');
+  }
+
   oneSignalInAppMessagingTriggerExamples() async {
     /// Example addTrigger call for IAM
     /// This will add 1 trigger so if there are any IAM satisfying it, it
@@ -365,6 +380,10 @@ class _MyAppState extends State<MyApp> {
                       height: 8.0,
                     )
                   ]),
+                  new TableRow(children: [
+                    new OneSignalButton("Get External User ID",
+                        _handleGetExternalId, !_enableConsentButton)
+                  ]),
                   new TableRow(children: [
                     new OneSignalButton("Set External User ID", _handleLogin,
                         !_enableConsentButton)
@@ -373,6 +392,10 @@ class _MyAppState extends State<MyApp> {
                     new OneSignalButton("Remove External User ID",
                         _handleLogout, !_enableConsentButton)
                   ]),
+                  new TableRow(children: [
+                    new OneSignalButton("Get OneSignal ID",
+                        _handleGetOnesignalId, !_enableConsentButton)
+                  ]),
                   new TableRow(children: [
                     new TextField(
                       textAlign: TextAlign.center,
diff --git a/ios/Classes/OSFlutterUser.m b/ios/Classes/OSFlutterUser.m
index 4e183136..698e25e1 100644
--- a/ios/Classes/OSFlutterUser.m
+++ b/ios/Classes/OSFlutterUser.m
@@ -47,6 +47,10 @@ + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
     if ([@"OneSignal#setLanguage" isEqualToString:call.method])
         [self setLanguage:call withResult:result];
+    else if ([@"OneSignal#getOnesignalId" isEqualToString:call.method])
+        [self getOnesignalId:call withResult:result];
+    else if ([@"OneSignal#getExternalId" isEqualToString:call.method])
+        [self getExternalId:call withResult:result];
     else if ([@"OneSignal#addAliases" isEqualToString:call.method])
         [self addAliases:call withResult:result];
     else if ([@"OneSignal#removeAliases" isEqualToString:call.method])
@@ -65,7 +69,8 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
         [self addSms:call withResult:result];
     else if ([@"OneSignal#removeSms" isEqualToString:call.method])
         [self removeSms:call withResult:result];
-    
+    else if ([@"OneSignal#lifecycleInit" isEqualToString:call.method])
+        [self lifecycleInit:call withResult:result];
     else
         result(FlutterMethodNotImplemented);
 }
@@ -132,4 +137,41 @@ - (void)removeSms:(FlutterMethodCall *)call withResult:(FlutterResult)result {
     result(nil);
 }
 
+- (void)lifecycleInit:(FlutterMethodCall *)call withResult:(FlutterResult)result {
+    [OneSignal.User addObserver:self];
+    result(nil);
+}
+
+- (void)onUserStateDidChangeWithState:(OSUserChangedState *)state {
+    NSString *onesignalId = [self getStringOrNSNull:state.current.onesignalId];
+    NSString *externalId = [self getStringOrNSNull:state.current.externalId];
+
+    NSMutableDictionary *result = [NSMutableDictionary new];
+    
+    NSMutableDictionary *currentObject = [NSMutableDictionary new];
+    
+    currentObject[@"onesignalId"] = onesignalId;
+    currentObject[@"externalId"] = externalId;
+    result[@"current"] = currentObject;
+
+    [self.channel invokeMethod:@"OneSignal#onUserStateChange" arguments:result];
+}
+
+- (void)getOnesignalId:(FlutterMethodCall *)call withResult:(FlutterResult)result {
+    result(OneSignal.User.onesignalId);
+}
+
+- (void)getExternalId:(FlutterMethodCall *)call withResult:(FlutterResult)result {
+    result(OneSignal.User.externalId);
+}
+
+/** Helper method to return NSNull if string is empty or nil **/
+- (NSString *)getStringOrNSNull:(NSString *)string {
+    // length method can be used on nil and strings
+    if (string.length > 0) {
+        return string;
+    } else {
+        return [NSNull null];
+    }
+}
 @end
diff --git a/lib/onesignal_flutter.dart b/lib/onesignal_flutter.dart
index e3938037..d9ad1724 100644
--- a/lib/onesignal_flutter.dart
+++ b/lib/onesignal_flutter.dart
@@ -48,6 +48,7 @@ class OneSignal {
   static void initialize(String appId) {
     _channel.invokeMethod('OneSignal#initialize', {'appId': appId});
     InAppMessages.lifecycleInit();
+    User.lifecycleInit();
     User.pushSubscription.lifecycleInit();
     Notifications.lifecycleInit();
   }
diff --git a/lib/src/user.dart b/lib/src/user.dart
index 4f040d2c..9889bc92 100644
--- a/lib/src/user.dart
+++ b/lib/src/user.dart
@@ -1,8 +1,45 @@
 import 'dart:async';
 import 'package:flutter/services.dart';
 
+import 'package:onesignal_flutter/src/utils.dart';
 import 'package:onesignal_flutter/src/pushsubscription.dart';
 
+typedef void OnUserChangeObserver(OSUserChangedState stateChanges);
+
+/// Represents the current user state with OneSignal.
+class OSUserState extends JSONStringRepresentable {
+  String? onesignalId;
+  String? externalId;
+
+  OSUserState(Map<String, dynamic> json) {
+    if (json.containsKey('onesignalId'))
+      this.onesignalId = json['onesignalId'] as String?;
+    if (json.containsKey('externalId'))
+      this.externalId = json['externalId'] as String?;
+  }
+
+  String jsonRepresentation() {
+    return convertToJsonString(
+        {'onesignalId': this.onesignalId, 'externalId': this.externalId});
+  }
+}
+
+/// An instance of this class describes a change in the user state.
+class OSUserChangedState extends JSONStringRepresentable {
+  late OSUserState current;
+
+  OSUserChangedState(Map<String, dynamic> json) {
+    if (json.containsKey('current'))
+      this.current = OSUserState(json['current'].cast<String, dynamic>());
+  }
+
+  String jsonRepresentation() {
+    return convertToJsonString(<String, dynamic>{
+      'current': current.jsonRepresentation(),
+    });
+  }
+}
+
 class OneSignalUser {
   static OneSignalPushSubscription _pushSubscription =
       new OneSignalPushSubscription();
@@ -12,6 +49,12 @@ class OneSignalUser {
   // private channels used to bridge to ObjC/Java
   MethodChannel _channel = const MethodChannel('OneSignal#user');
 
+  List<OnUserChangeObserver> _observers = <OnUserChangeObserver>[];
+  // constructor method
+  OneSignalUser() {
+    this._channel.setMethodCallHandler(_handleMethod);
+  }
+
   /// Sets the user's language.
   ///
   /// Sets the user's language to [language] this also applies to
@@ -111,4 +154,45 @@ class OneSignalUser {
   Future<void> removeSms(String smsNumber) async {
     return await _channel.invokeMethod("OneSignal#removeSms", smsNumber);
   }
+
+  /// Returns the nullable External ID for the current user.
+  Future<String?> getExternalId() async {
+    return await _channel.invokeMethod("OneSignal#getExternalId");
+  }
+
+  /// Returns the nullable OneSignal ID for the current user.
+  Future<String?> getOnesignalId() async {
+    return await _channel.invokeMethod("OneSignal#getOnesignalId");
+  }
+
+  /// Add an observer that fires when the OneSignal User state changes.
+  /// *Important* When using the observer to retrieve the onesignalId, check the
+  /// externalId as well to confirm the values are associated with the expected user.*
+  void addObserver(OnUserChangeObserver observer) {
+    _observers.add(observer);
+  }
+
+  // Remove a user state observer that has been previously added.
+  void removeObserver(OnUserChangeObserver observer) {
+    _observers.remove(observer);
+  }
+
+  Future<void> lifecycleInit() async {
+    return await _channel.invokeMethod("OneSignal#lifecycleInit");
+  }
+
+  // Private function that gets called by ObjC/Java
+  Future<Null> _handleMethod(MethodCall call) async {
+    if (call.method == 'OneSignal#onUserStateChange') {
+      this._onUserStateChange(
+          OSUserChangedState(call.arguments.cast<String, dynamic>()));
+    }
+    return null;
+  }
+
+  void _onUserStateChange(OSUserChangedState stateChanges) async {
+    for (var observer in _observers) {
+      observer(stateChanges);
+    }
+  }
 }