| Bretislav I | |
|---|---|
 12th-century fresco depiction in the Znojmo Rotunda | |
| Duke of Bohemia | |
| Reign | 1034 – 10 January 1055 |
| Predecessor | Oldřich |
| Successor | Spytihněv II |
| Born | between 1002 and 1005 |
| Died | 10 January 1055 (aged c. 50–53) Chrudim |
| Spouse | Judith of Schweinfurt |
| Issue | Spytihněv II, Duke of Bohemia Vratislaus II of Bohemia Conrad I, Duke of Bohemia Otto I of Olomouc Jaromír, Bishop of Prague |
| Dynasty | Přemyslid |
| Father | Oldřich of Bohemia |
| Mother | Božena |
Bretislav I (Czech: Břetislav I.; 1002/1005 – 10 January 1055), known as the "Bohemian Achilles", of the Přemyslid dynasty, was Duke of Bohemia from 1034 until his death in 1055.