In the original Assassin's Creed, what is the name of the assassin controlled by the player?

The player-controlled assassin in the original Assassin's Creed is Altaïr Ibn-La'Ahad.

Altaïr is the central character of the 2007 game and a senior member of the Assassin Brotherhood during the Third Crusade. His name is Arabic for “the flyer” or “the soaring one,” while Ibn-La'Ahad means “son of no one.” The story follows his fall from grace after a failed mission and his gradual restoration of rank through a series of investigations and assassinations.

The game presents Altaïr through Desmond Miles’s genetic memories, experienced with the Animus. This framing device allows the modern-day story and the historical setting to share the same game. Altaïr is often confused with Ezio Auditore, who became the leading playable assassin in the next major era of the series, beginning with Assassin's Creed II.

Altaïr later appears in Assassin's Creed Revelations, where Ezio investigates his life and legacy. That later appearance connects the first game's protagonist to the broader mythology of the franchise.