In the United States Armed Forces, a unified command (or "unified defense command") is a large collection of combat groups from the four armed forces (Army, Navy, Air Force, and Marines).

This system was created by the same National Security Act of 1947 that created the Department of Defense, and was modified significantly by the Goldwater-Nichols Act of 1986. Its intention during the Cold War was to create a command structure for a hypothetical multi-front war with the Soviet Union. Since then, its structure has been modified several times to reflect changing American defense priorities, most recently with the 2002 addition of the Northern Command for homeland security purposes.

Today, there are nine unified commands. Five have responsibility for specifically defined regions of the globe, while the other four have more general responsibilities. As of 2002, the unified commands, their jurisdictions, and headquarters are: