Which studio was the primary developer of the original Assassin's Creed game?

Ubisoft Montreal was the primary developer of the original Assassin's Creed game.

The Montreal studio led production of the first mainline title, working with other Ubisoft teams on technology, art, testing, and additional development. The game was directed by Patrice Désilets, with Jade Raymond serving as producer. Its design built on ideas associated with the Prince of Persia series while creating a new historical stealth-action franchise.

Ubisoft Montreal's work established several features that became series signatures: open historical cities, social stealth, freerunning across buildings, assassination investigations, and a modern-day narrative surrounding the Animus. The studio's version of the medieval Levant includes cities such as Jerusalem, Acre, and Damascus.

Ubisoft Quebec is a frequent mix-up because it later led development of Assassin's Creed Odyssey. Ubisoft Sofia also contributed to later franchise projects, including Assassin's Creed Rogue and Liberation-related work. Those studios were important to the wider series, but Montreal was the primary developer of the original game.