Casimir I | |
|---|---|
 Coat-of-arms of Upper Silesia (Opole, Cieszyn, etc.) | |
| Born | 1280/90 |
| Died | c. 29 September 1358 |
| Noble family | Silesian Piasts of Opole |
| Spouse(s) | Euphemia of Czersk |
| Issue | Władysław of Cieszyn Jolanta Helena Bolesław Przemyslaus I Noszak Agnes Jan of Cieszyn Siemowit of Cieszyn Elisabeth of Cieszyn |
| Father | Mieszko I, Duke of Cieszyn |
| Mother | ?Grzymisława Vsevolodovna of Belz |
Casimir I of Cieszyn (Polish: Kazimierz I cieszyński, Czech: Kazimír I. Těšínský, German: Kasimir I. von Teschen; 1280/90 – c. 29 September 1358), was Duke of Cieszyn from 1315, Duke of Siewierz from 1337 and Duke of Bytom from 1357.
He was the second son of Mieszko I, Duke of Cieszyn by his wife, probably called Grzymisława.