Trojden I (1284/86[1] – 13 March 1341) was a Polish prince, Duke of Czersk from 1310, ruler over Warsaw and Liw from 1313, and regent of Płock in the years 1336–1340.

Trojden was the second son of Bolesław II of Płock and his first wife Gaudemantė (Sophia), the daughter of Grand Duke Traidenis of Lithuania.

In 1323, when the Rurikid dynasty in Ruthenia became extinct after the death of Andrew of Galicia, Trojden I was able to place on the throne his oldest son Bolesław, who assumed the name Yuri II (in honour of his maternal grandfather).

On 2 January 1326, Trojden I and his brothers concluded an agreement with the Teutonic Order at Brodnica, which led to a short conflict with Poland and its ally Lithuania.

[3] In 1859, his remains were transferred to the Church of Our Lady of Carmel in Warka, thanks to the initiative of Piotr Wysocki, as manifestation of growing Polish nationalism.