The Nagai clan (永井氏, Nagai-shi), was a prominent samurai and aristocratic lineage in Japan. During the Sengoku period, they served under the Tokugawa clan and in the Edo period, three branches of the clan became hereditary daimyō, and following the Meiji Restoration, all three branches were ennobled as viscount (子爵, shishaku) families within the peerage system.
| Nagai clan 永井氏 | |
|---|---|
 | |
| Home province | Mikawa Province |
| Titles | Samurai, Peerage |
| Founder | Nagai Naokatsu |
| Final ruler | Various |
| Founding year | 1616 |