| Usuki Castle Japanese: 臼杵城 | |
| Location: | Usuki, Ōita Prefecture, Japan |
| Type: | Japanese castle |
| Built: | 1562 |
| Builder: | Ōtomo Sōrin |
| Coordinates: | 33.1218°N 131.8041°W |
| Pushpin Map: | Japan |
is a Japanese castle in Usuki, Ōita Prefecture, Japan. Another name of this castle is .
This castle was constructed by Ōtomo Sōrin in 1562 on the island Nyū-jima, in Usuki Bay as his head castle. During the 1560s, Sōrin had the largest territory in Kyūshū. However, after defeat at the Battle of Mimigawa in 1578, the power of Sōrin and the Ōtomo clan rapidly declined. In 1586, this castle fell to Shimazu Yoshihiro, a daimyō of Kagoshima, but was rescued by Toyotomi Hideyoshi.