Altaïr's story in the first Assassin's Creed game is set during the Third Crusade.
The Third Crusade took place from 1189 to 1192, after the capture of Jerusalem by Saladin in 1187. Assassin's Creed uses this period as the historical framework for Altaïr Ibn-La'Ahad's missions. The game presents a fictional story involving the Assassin Brotherhood, the Templars, and political figures from the era.
Altaïr travels among major cities including Jerusalem, Acre, and Damascus. These locations are reconstructed as game environments rather than exact historical replicas. The narrative places fictional targets alongside real leaders such as Richard the Lionheart and Saladin.
The setting is often confused with other Crusades because the series later visits many different eras. Assassin's Creed itself does not depict the First, Second, or Fourth Crusade as its main period; Altaïr's campaign belongs specifically to the Third Crusade.