Masyaf is a city in northwestern Syria. It is the center of the Masyaf District in the Hama Governorate. As of 2004, Masyaf had a religiously diverse population of approximately 22,000 Ismailis, Alawites and Christians. The city is well known for its large medieval castle, particularly its role as the headquarters of the Nizari Ismailis and their elite Assassins unit.