Garmdarreh is a city located in the Central District of Karaj County within the Alborz province of Iran. It serves as the administrative center for the Garmdarreh Rural District.
The city was established in 2004 following a merger of several surrounding areas. The village of Garmdarreh combined with the villages of Kuhak, Amirabad, Qaleh-ye Salar Nasriyeh-ye Garmdarreh, Sa'adatiyeh-ye Qadim, and Sa'adatiyeh-ye Now to form the current municipal entity.