Gregory Tsamblak (Bulgarian: Григорий Цамблак; Greek: Γκρέγκορι Τζαμπλάκων; Romanian: Grigorie Țamblac; Serbian Cyrillic: Григорије Цамблак; Ukrainian: Григорій Цамблак; c. 1365 – c. 1420), member of the Tzamplakon family, was a writer and cleric active in Bulgaria, Moldavia, Serbia, Grand Duchy of Lithuania, and the Principality of Kiev.