In Assassin's Creed, which historical period is the setting for Altaïr's story?

Altaïr's story in Assassin's Creed is set during the Third Crusade.

The game's historical sequences occur in 1191, when Altaïr Ibn-La'Ahad works for the Assassin Brotherhood in cities including Masyaf, Acre, Damascus, and Jerusalem. The campaign uses real Crusades-era locations while combining documented history with fictional characters, secret organizations, and supernatural technology.

The Third Crusade lasted from 1189 to 1192 and followed the capture of Jerusalem by Saladin in 1187. Major historical figures associated with the campaign included Saladin, Richard I of England, and Philip II of France. Assassin's Creed places Altaïr inside this political and military world without presenting its plot as a literal historical record.

The period is sometimes confused with the Renaissance setting of Assassin's Creed II. That later game moves forward several centuries and follows Ezio Auditore da Firenze in fifteenth- and sixteenth-century Italy.