Call of Duty 4: Modern Warfare (often abbreviated to COD4) is a first-person shooter developed by Infinity Ward and published by Activision for Xbox 360, PlayStation 3 and Windows. It is the fourth installment in the Call of Duty video game series (excluding expansions), but the first one to break away from the World War II setting and be set in modern times, and the first game in the series to be rated Mature in North America. The title and game details were announced on April 25, 2007. It was released worldwide between November 6 2007 and November 9, 2007, and became available on Steam on November 6 2007 for pre-purchase, becoming available to play on November 12 2007. A Mac OS X version of the game is scheduled to be released in May 2008. The game has received almost universal praise, winning multiple awards at gaming websites, and has been complimented on its storyline, visual elements, realism, and quality of its multiplayer.

The story is set in a fictional near-future war between the U.S., Europe, and Russian Loyalists against Russian Ultranationalists and Middle Eastern rebels, and features many real-world weapons and vehicles. It is told from the perspective of both a US Marine and an operative of the British SAS, and is set in a variety of locations, including the Middle East, Azerbaijan, Russia, and Prypiat. Its multiplayer features a variety of game modes and contains a "level/ranking" system, with the player unlocking additional weapons, weapon attachments, and camouflage schemes as they advance.