Casimir IV KG (Polish: Kazimierz IV Jagiellończyk; Lithuanian: Kazimieras IV Jogailaitis; 30 November 1427 – 7 June 1492) of the House of Jagiellon is Grand Duke of Lithuania from 1440, and King of Poland from 1447, until his death.

Casimir is the second son of King Władysław II Jagiełło (Jogaila), and the younger brother of Władysław III of Varna.