John Ernest I, Duke of Saxe-Weimar
| John Ernest I | |
|---|---|
Portrait by Michiel Jansz. van Mierevelt | |
| Duke of Saxe-Weimar | |
| Reign | 1605–1620 |
| Predecessor | Johann |
| Successor | Wilhelm |
| Born | 21 February 1594 Altenburg |
| Died | 6 December 1626 (aged 32) Sankt Martin, Hungary |
| House | House of Wettin |
| Father | Johann, Duke of Saxe-Weimar |
| Mother | Dorothea Maria of Anhalt |
| Religion | Lutheran |
Johann Ernst I, Duke of Saxe-Weimar (21 February 1594 in Altenburg – 6 December 1626 in Sankt Martin, Hungary), was a duke of Saxe-Weimar.