diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74ef8c00d2..7fbc93f2a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,7 +5,8 @@
 
 ### Enhancements
 * [Sync] Added option to use managed WebSockets via OkHttp instead of Realm's built-in WebSocket client for Sync traffic (Only Android and JVM targets for now). Managed WebSockets offer improved support for proxies and firewalls that require authentication. This feature is currently opt-in and can be enabled by using `AppConfiguration.usePlatformNetworking()`. Managed WebSockets will become the default in a future version. (PR [#1528](https://github.com/realm/realm-kotlin/pull/1528)).
-* `AutoClientResetFailed` exception now reports as the throwable cause any user exceptions that might occur during a client reset. (Issue [#1580](https://github.com/realm/realm-kotlin/issues/1580))
+* [Sync] `AutoClientResetFailed` exception now reports as the throwable cause any user exceptions that might occur during a client reset. (Issue [#1580](https://github.com/realm/realm-kotlin/issues/1580))
+* [Sync] Added a new `SyncSessionAuthExpired` exception subclass that will be sent to the `SyncConfiguration.errorHandler` if the sync session is stopped because the users refresh token is no longer valid and they need to log in again. (Isse [#1640](https://github.com/realm/realm-kotlin/issues/1640))
 
 ### Fixed
 * Cache notification callback JNI references at startup to ensure that symbols can be resolved in core callbacks. (Issue [#1577](https://github.com/realm/realm-kotlin/issues/1577))
diff --git a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/exceptions/SyncExceptions.kt b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/exceptions/SyncExceptions.kt
index 2e6806062d..964cd1cf47 100644
--- a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/exceptions/SyncExceptions.kt
+++ b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/exceptions/SyncExceptions.kt
@@ -63,6 +63,18 @@ public class WrongSyncTypeException internal constructor(message: String) : Sync
 public class BadFlexibleSyncQueryException internal constructor(message: String) :
     SyncException(message)
 
+/**
+ * Thrown when the sync sessions access token expires and it isn't possible to renew it
+ * automatically because the users refresh token is no longer valid.
+ *
+ * Device Sync is stopped and can only be resumed after closing the realm, logging the user
+ * back in and reopen the realm by using the new user object.
+ *
+ * @see https://www.mongodb.com/docs/atlas/app-services/users/sessions/
+ */
+public class AuthExpiredException internal constructor(message: String) :
+    SyncException(message)
+
 /**
  * Thrown when the server undoes one or more client writes. Details on undone writes can be found in
  * [writes].
diff --git a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/RealmSyncUtils.kt b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/RealmSyncUtils.kt
index fb72304c78..5568b7ac77 100644
--- a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/RealmSyncUtils.kt
+++ b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/RealmSyncUtils.kt
@@ -8,6 +8,7 @@ import io.realm.kotlin.internal.interop.sync.AppError
 import io.realm.kotlin.internal.interop.sync.SyncError
 import io.realm.kotlin.mongodb.exceptions.AppException
 import io.realm.kotlin.mongodb.exceptions.AuthException
+import io.realm.kotlin.mongodb.exceptions.AuthExpiredException
 import io.realm.kotlin.mongodb.exceptions.BadFlexibleSyncQueryException
 import io.realm.kotlin.mongodb.exceptions.BadRequestException
 import io.realm.kotlin.mongodb.exceptions.CompensatingWriteException
@@ -79,6 +80,7 @@ internal fun convertSyncError(syncError: SyncError): SyncException {
     val errorCode = syncError.errorCode
     val message = createMessageFromSyncError(errorCode)
     return when (errorCode.errorCode) {
+        ErrorCode.RLM_ERR_AUTH_ERROR -> AuthExpiredException(message)
         ErrorCode.RLM_ERR_WRONG_SYNC_TYPE -> WrongSyncTypeException(message)
 
         ErrorCode.RLM_ERR_INVALID_SUBSCRIPTION_QUERY -> {