Bolesław the Pious () (1224/27 – 14 April 1279) was a Duke of Greater Poland during 1239–1247 (according to some historians during 1239–1241 sole Duke of Ujście), Duke of Kalisz during 1247–1249, Duke of Gniezno during 1249–1250, Duke of Gniezno-Kalisz during 1253–1257, Duke of whole Greater Poland and Poznań during 1257–1273, in 1261 ruler over Ląd, regent of the Duchies of Mazovia, Płock and Czersk during 1262–1264, ruler over Bydgoszcz during 1268–1273, Duke of Inowrocław during 1271–1273, and Duke of Gniezno-Kalisz from 1273 until his death.