Louis IX, Landgrave of Hesse-Darmstadt
| Louis IX | |
|---|---|
| Landgrave of Hesse-Darmstadt | |
| Reign | 12 October 1768 – 6 April 1790 |
| Predecessor | Louis VIII |
| Successor | Louis X |
| Born | 15 December 1719 Darmstadt |
| Died | 6 April 1790 (aged 70) Pirmasens |
| Spouses | Marie Adelaide of Cheirouze, Countess of Lemberg
(m. 1775) |
| Issue | |
| House | Hesse-Darmstadt |
| Father | Louis VIII, Landgrave of Hesse-Darmstadt |
| Mother | Countess Charlotte of Hanau-Lichtenberg |
Louis IX of Hesse-Darmstadt (German: Ludwig) (15 December 1719 – 6 April 1790) was Landgrave of Hesse-Darmstadt from 1768 to 1790.