Casimir I of Kuyavia (Polish: Kazimierz I kujawski; c. 1211 – 14 December 1267) was a Polish prince and a member of the House of Piast. He was Duke of Kujawy after 1233, ruler over Ląd from 1239-1261, ruler over Wyszogród after 1242, Duke of Sieradz from 1247-1261, Duke of Łęczyca after 1247, and Duke of Dobrzyń after 1248.
He was the second son of Konrad I of Masovia and his wife Agafia of Rus. He was probably named after his grandfather, Casimir II the Just.
Władysław I Łokietek, in English known as the "Elbow-high" or Ladislaus the Short (c. 1260/1 – 2 March 1333), was King of Poland from 1320 to 1333, and duke of several of the provinces and principalities in the preceding years. He was a member of the royal Piast dynasty, the son of Duke Casimir I of Kuyavia, and great-grandson of High-Duke Casimir II the Just.
Władysław I inherited a small portion of his father's domain, but his dominion grew as some of his brothers died young. He unsuccessfully tried to incorporate the Duchy of Kraków (the Seniorate Province) in 1289, following the death of his half-brother Leszek II the Black and the withdrawal from contention of his ally Bolesław II of Masovia. After a period in exile during the rule of Wenceslaus II, Władysław regained several duchies and then Kraków in 1306 when Wenceslaus III was murdered. He temporarily took control of part of Greater Poland after the death of his ally Przemysł II, lost it, and then regained it.