Casimir "the Just" (
1138-
1194;
Polish:
Kazimierz Sprawiedliwy) of the
Piast dynasty was the youngest son of
Boleslaus III of Poland. He reigned as
duke of
Krakow and senior
prince of
Poland (see
Seniorate[?]) from
1177 until his death. Born shortly before or after his father's death, and omitted (possibly for that reason) from Boleslaus's will dividing the kingdom between Casimir's four elder brothers, he set about securing the territorial basis for a claim to power, gaining the dukedom of Wislica in 1167 and of Sandomierz in
1173. In
1180 he won acceptance by the nobility and clergy of the principle of hereditary succession to the Krakow dukedom, though it would take more than a century to restore the Polish kingship.