| Hosokawa Mitsunao 細川 光尚 | |
| Nationality: | Japanese |
| Order: | Head of Kumamoto-Hosokawa clan |
| Term Start: | 1641 |
| Term End: | 1650 |
| Predecessor: | Hosokawa Tadatoshi |
| Successor: | Hosokawa Tsunatoshi |
| Order1: | Daimyō of Kumamoto |
| Term Start1: | 1641 |
| Term End1: | 1650 |
| Predecessor1: | Hosokawa Tadatoshi |
| Successor1: | Hosokawa Tsunatoshi |
| Birth Date: | October 26, 1619 |
| Father: | Hosokawa Tadatoshi |
| Battles: | Shimabara Rebellion (1637) |
was a Japanese daimyō of the early Edo period. He was the grandson of the famous Christian convert (Kirishitan), Hosokawa Gracia. His great-grandfather was Hosokawa Fujitaka. His childhood name was Rokumaru (六丸).
Mitsunao was born in 1619, and was the eldest son of Hosokawa Tadatoshi.
In 1637, he joined his father in the effort to subdue the Shimabara Rebellion, and fought with distinction.
Succeeding his father in 1641, he became daimyō of the Kumamoto Domain.
Mitsunao's suppression of the Abe family's revolt in 1642 is famous, due to its fictionalization by Mori Ōgai.