What was Assassin's Creed originally planned as a sequel to?

Assassin's Creed was originally planned as a sequel to Prince of Persia: The Sands of Time.

During development, the project began as a Prince of Persia concept known as Prince of Persia: Assassins. The design increasingly focused on a new protagonist, freer exploration, and the historical Assassin tradition, eventually becoming its own intellectual property.

This origin explains several connections between the franchises. Both series emphasize acrobatic movement, climbing, and traversal across historical environments. However, Assassin's Creed added the Animus framework, a modern-day storyline, and the long-running Assassin-Templar conflict.

The earlier Prince of Persia game was released in 2003 and followed the Prince through a fantasy version of ancient Persia. Assassin's Creed instead launched in 2007 with Altaïr during the Third Crusade. The two games share design ancestry, but they are separate franchises.