Tom Clancy's Splinter Cell: Chaos Theory is a stealth game developed by Ubisoft Montreal and Ubisoft Milan and released in March 2005 for the Xbox.

Chaos Theory is the third game in the Splinter Cell series endorsed by novelist Tom Clancy. As with previous entries in the franchise, Chaos Theory follows the activities of Sam Fisher, an agent working for a covert-ops branch within the NSA called "Third Echelon". The game has a significantly darker tone than its predecessors, featuring more combat and the option for Fisher to kill people he interrogates as opposed to merely knocking them out. As a result, it was the first Splinter Cell game to receive an M-rating by the ESRB, an assessment which has since been applied to all subsequent releases in the series. Actor Michael Ironside reprised his role as Fisher, while Don Jordan returned from the original game to voice Third Echelon director Irving Lambert and Claudia Besso returned as hacker and analyst Anna Grímsdóttir having both been replaced by Dennis Haysbert and Adriana Anderson respectively in Tom Clancy's Splinter Cell: Pandora Tomorrow.