Who created the original Assassin's Creed game concept?

Patrice Désilets created the original Assassin's Creed game concept.

Désilets is a Canadian video game designer who worked at Ubisoft Montreal and served as creative director on the first Assassin's Creed. The project grew from ideas developed after Prince of Persia: The Sands of Time, including a larger open world, freer movement, and a story involving a secretive order of Assassins.

The finished game was developed by a large team, so creation was a collaborative production rather than the work of one person alone. Jade Raymond served as producer, and Corey May wrote the screenplay for the first game. Those roles are why several names are often associated with the title's development.

Désilets later worked on Assassin's Creed II before leaving Ubisoft. He subsequently co-founded Panache Digital Games and directed Ancestors: The Humankind Odyssey. The distinction between creator, producer, writer, and publisher helps identify the specific answer to this question.