United States Space Command (USSPACECOM or SPACECOM) is a unified combatant command of the United States Department of Defense, responsible for military operations in outer space, specifically all operations 100 kilometers (62 miles) and greater above mean sea level. U.S. Space Command is responsible for the operational employment of space forces that are provided by the uniformed services of the Department of Defense.

Space Command was originally created in September 1985 to provide joint command and control for all military forces in outer space and coordinate with the other combatant commands. SPACECOM was disestablished in 2002, and its responsibilities and forces were merged into United States Strategic Command. It was reestablished on 29 August 2019, with a reemphasized focus on space as a warfighting domain.

The U.S. Space Force is the military service responsible for organizing, training, and equipping the majority of forces for U.S. Space Command, which also includes a smaller number of forces from each of the other branches of the U.S. Armed Forces.

U.S. Space Command, working with allies and partners, plans, executes, and integrates military spacepower into multi-domain global operations in order to deter aggression, defend national interests, and when necessary, defeat threats.

U.S. Space Command has four "space truths" that provide the foundation for its vision and operations:

Early military space activities were predominantly focused on research and development, rather than operations, and split across the Air Force, Army, and Navy. In 1959, Admiral Arleigh Burke proposed the creation of the Defense Astronautical Agency to control all military space programs. This proposal was supported by the Army and Navy, but opposed by the Air Force.

Arguing that space defense was an extension of air defense, the Joint Chiefs of Staff ultimately agreed with the Air Force, putting operational control of space defense forces under the unified Continental Air Defense Command and multinational North American Air Defense Command in 1960. In 1975, Continental Air Defense Command was inactivated and replaced with Aerospace Defense Command (ADCOM), a specified command led by the Air Force. In 1981, North American Air Defense Command changed its name to North American Aerospace Defense Command to better reflect its role in both air and space defense.

The Reagan Administration's Strategic Defense Initiative brought a new focus on space. In 1983, General James V. Hartinger, the commander of Aerospace Defense Command and Air Force Space Command, proposed movement towards a unified space command. The Air Force supported a unified command, which would be dominated by the aerospace service, however, the Army, Navy, and Marine Corps were satisfied with the current arrangement. However, the White House supported the Air Force's position that a unified command should be created, and on 20 November 1984, President Ronald Reagan approved its establishment. U.S. Space Command's missions would include integrating tactical warning and space operations, including control of space, direction of space support activities, and planning for ballistic missile defense. U.S. Space Command would also replace Aerospace Defense Command as the supporting U.S. command to North American Aerospace Defense Command, sharing the same commander.