Konrad II of Czersk (pl: Konrad II czerski; c. 1250 – 24 June/21 October 1294[1]), was a Polish prince member of the House of Piast, Duke of Masovia during 1264-1275 jointly with his brother, after 1275 sole ruler over Czersk and Duke of Sandomierz during 1289.
He was the eldest son of Siemowit I of Masovia and Pereyaslava, a Russian princess.
- ^ Jasiński, Kazimierz (1998). Rodowód Piastów mazowieckich. Poznań - Wrocław: Wydawnictwo Historyczne. p. 15. ISBN 83-913563-0-2. assumed that both dates are equally likely