Call of Duty 4: Modern Warfare is a first-person shooter video game developed by Infinity Ward and published by Activision for Xbox 360, PlayStation 3, and Windows. It is scheduled for release for Mac OS X in May 2008. It is the fourth installment of the Call of Duty video game series, excluding expansion packs. The game breaks away from the World War II setting of previous games in the series and is instead set in modern times. The game is the first in the series to be rated Mature in North America. The title and game details were announced on April 25, 2007, and the game was released worldwide between November 6, 2007 and November 9, 2007. It became available on Steam on November 6, 2007 for pre-purchase, and was available to play on November 12, 2007.

The story is set in a fictional near-future war between the United States, the United Kingdom, and Russian Loyalists against Russian Ultranationalists and Middle Eastern rebels. It is told from the perspectives of a United States Marine and a member of the British SAS, and is set in multiple locations, including the Middle East, Azerbaijan, Russia, and Prypiat, Ukraine. The multiplayer portion of the game features various game modes, and contains a leveling system that allows the player to unlock additional weapons, weapon attachments, and camouflage schemes as they advance. The game was in development for two years. It uses a proprietary game engine, and includes features that include true world-dynamic lightning, HDR lighting effects, dynamics shadows, and depth of field.

Call of Duty 4: Modern Warfare received considerable praise and has won numerous awards from gaming websites, including IGN's "Best Xbox 360 Game". It was the top-selling game worldwide for 2007, reaching over than seven million copies as of January 2008.