What is the name of the Animus user's modern-day ancestor in the first Assassin's Creed?

Altaïr Ibn-La'Ahad is the ancestor whose memories Desmond Miles experiences in the first Assassin's Creed.

Altaïr is a Syrian Assassin active during the Third Crusade. At the beginning of the game, he is a highly skilled but overconfident member of the Brotherhood. After a failed mission, he is demoted and must regain his rank by pursuing targets across the Holy Land.

The Animus allows Desmond to access genetic memories inherited from his ancestors. This framing device links the modern-day storyline with Altaïr's historical missions in Jerusalem, Acre, and Damascus.

Altaïr is distinct from Ezio, who becomes the central ancestor in Assassin's Creed II. His name is also commonly rendered with different transliteration marks, but “Altaïr Ibn-La'Ahad” is the standard English form used for the character.