Xenosaga: Pied Piper is a role-playing video game co-developed by Monolith Soft, Namco Mobile, and Tom Create. The game was published by Namco in 2004 for mobile devices.

The game was only released in Japan, originally in 2004 as 6 Vodafone apps, starting on July 14th and fully released on October 13th. They were available as 3 chapter purchases, each split into 2 parts released within weeks of each other.
The game was made available for i-mode devices on July 6th 2006, through Namco's monthly subscription service.