10th-century Polish monarchs

first King of Poland (967–1025)

Duke of Poland

Siemomysł or Ziemomysł ( – ) was the third duke of the Polans and the father of Poland's first Christian ruler, Mieszko I. A member of the Piast dynasty, he was listed by Gallus Anonymous in his Gesta principum Polonorum as the son of Lestek, the second known duke of the Polans. According to Gallus' account and historical research, Siemomysł has been credited with leaving the lands of the Polans, Goplans and Masovians to his son Mieszko I, who further expanded them during his reign.

Lestek (also Leszek, Lestko) was the second duke of Polans, and son of Siemowit, born c. 870–880, mentioned in the oldest Polish chronicle, Gesta principum Polonorum by Gallus Anonymus. The dukes of Polans were the foundation of the Piast dynasty, the first historical ruling dynasty of Poland.