Bolesław III Wrymouth

Bolesław III Wrymouth (1086–1138) was duke of Poland from 1107. The son of Władysław I Herman, he and his half-brother Zbigniew expelled the palatine Sieciech in 1101 and divided the realm on their father's death in 1102. He later blinded Zbigniew, then did public penance and pilgrimaged to Hungary.

Alliances with Hungary and Kievan Rus helped him repel an imperial invasion in 1109. From 1113 he conquered Pomerania in stages, incorporating Gdańsk Pomerania and supporting Otto of Bamberg's missions; in 1135 at the Congress of Merseburg he settled Pomerania's status with the Empire. His testament divided Poland among his sons, causing two centuries of fragmentation.