Siemowit of Dobrzyń
Siemowit of Dobrzyń (c. 1262–1312) was a Piast prince, son of Casimir I of Kuyavia, who received the Dobrzyń district in the family division of around 1288. Captured by Lithuanian raiders in 1293, he spent two years in captivity while his brother Władysław I ruled the duchy. Around 1296 he married Anastasia.
He did homage to Wenceslaus II of Bohemia in 1300, was deposed in 1303 and restored in 1305, after which he backed Władysław. He died in 1312, leaving minor sons under the regency of his widow and brother.