Call of Duty: United Offensive is an expansion pack for the popular first person shooter computer game, Call Of Duty. It is developed by Gray Matter Interactive, with contributions from Pi Studios, and published by Activision. It was released for Microsoft Windows on September 14th, 2004.

The game features single-player missions centered around the three major Allied forces of World War II: the United States (as Cpl. Scott Riley), the United Kingdom (as Sgt. James Doyle) and the Soviet Union (as Pvt. Yuri Petrenko), and includes historical battles such as the Battle of the Bulge, Battle of Kursk, and the invasion of Sicily. A minor deviation from the original game is a bombing mission in which the player mans several M2 Browning machine guns. Several new abilities are added to the game as well, including the ability to deploy light machine guns, use flamethrowers, to sprint; which makes the character run faster but at the cost of not being able to fire their weapon, and the ability to cook grenades.

The biggest changes made by United Offensive are in the multiplayer aspect of the game. There are new maps which are much larger than the ones in the original game, new weapons from the single player campaign, an in-game rank system which grants additional bonuses with more points, and vehicles such as tanks and jeeps (similar to "Battlefield 1942").