Provisional Council of the Duchy of Masovia
The Provisional Council of the Duchy of Masovia (Polish: Rada Zastępcza Tymczasowa Księstwa Mazowieckiego) was a government ad interim of Warsaw and the Masovian Voivodeship, liberated in the Warsaw Insurrection during the Kościuszko Uprising. It was headed by Ignacy Wyssogota Zakrzewski, president of Warsaw.
Source: Wikipedia — Provisional Council of the Duchy of Masovia (CC BY-SA 4.0)