The Command/Service Module (CSM) was one of two spacecraft, along with the Lunar Module, used for the United States Apollo program which landed astronauts on the Moon. It was built for NASA by North American Aviation. It was launched by itself into suborbital and low Earth orbit test missions with the Saturn IB launch vehicle, and three times by itself and nine times with the Lunar Module as part of the Apollo spacecraft assembly on the larger Saturn V launch vehicle, which was capable of sending it to the Moon.

After the Apollo lunar program, the CSM saw manned service as a crew shuttle for the Skylab program, and the Apollo-Soyuz Test Project in which an American crew rendezvoused and docked with a Soviet Soyuz spacecraft in Earth orbit.

The CSM consisted of two segments: the Command Module, a cabin which housed a crew of three and equipment needed for re-entry and splashdown; and a Service Module that provided propulsion, electrical power and storage for various consumables required during a mission. The Service Module was cast off and allowed to burn up in the atmosphere before the Command Module re-entered and brought the crew home.