The original Assassin's Creed is mainly set in 1191, during the Third Crusade. Altaïr Ibn-La'Ahad carries out missions in historically inspired cities including Masyaf, Jerusalem, Acre, and Damascus.
The year places the story during the conflict between forces associated with the European Crusader states and Saladin's Ayyubid army. The game uses real political and military figures, but its secret Assassin and Templar conflict is fictionalized.
Players sometimes confuse this date with the eras of later games. Assassin's Creed Origins is set in the first century BCE, while Assassin's Creed II begins in Renaissance Italy. The original game's 1191 setting is therefore an early medieval period, not the Renaissance.
The opening historical setting also helps explain the game's architecture, weapons, faction politics, and emphasis on fortified cities. Its version of history is designed for adventure rather than strict documentary accuracy, but the date and broad Crusade-era context are central to the game's identity.