Was Altair a real person

Altair was a real assassin because Ezio Auditoré Da Firenze is real.

it says based on various RELIGIONS & BELIEFS.. but also in Assassins Creed 2 after you beat the game you can obtain his armor by visiting all the assassin's tombs.. still he sounds pretty awesome to me

The concept of Assassins Creed is very fictional but historians have discovered that there was an assassin's brotherhood based in a place called Masyaf, which is a castle in modern day Syria. Most of the records there were burnt after the third crusade. And all the assassin characters are fictional but there was a man called Rashid ad-Din Sinan portrayed as Al Mualim people named him the mas of the Masyaf mountain. And he believed that there would be a profit to stop the crusade this person is portrayed as Altair. And he had a list of 9 people to assassinate in order to stop the war and he (apparently did help the end of it) did it. and nobody and prove what happened because all the documents and Masyaf, Syria were burnt and disposed of, probably to hide the evidence of assassins.