Trojden I of Masovia

Trojden I (1284/1286 – 13 March 1341) was a Piast duke who ruled Czersk from 1310 and, after his father Bolesław II of Płock died in 1313, Warsaw and Liw as well, giving him all of eastern Masovia. Around 1310 he married Maria, daughter of Yuri I of Halych-Volhynia.

When the Rurikid line ended in 1323, he placed his son Bolesław on the Ruthenian throne as Yuri II. He maneuvered between Poland and the Teutonic Order, joining the Order in 1326, and in 1340 sold his Ruthenian claim to Casimir III after Yuri II was poisoned.