| Kuh Qaen castle | |
| Native Name: | قلعه کوه قائن |
| Location Town: | Qaen |
| Location Country: | Iran |
| Building Type: | Castle |
Kuh Qaen castle or Ghal'eh-Kuh of Qa'en (Persian: قلعه کوه قائن), also known as Husayn Qa'ini Castle (Persian: قلعه جسین قائنی), is a historical castle located in Qaen County in South Khorasan Province, The fortress dates back to the Ismailis of the Alamut Period.[1] [2] It was one of their most important strongholds in Quhistan.