Skylab 4 (also SL-4 and SLM-3) was the third Skylab mission and placed the third and final crew on board the space station. The mission started November 16, 1973 with the launch of three astronauts on a Saturn IB rocket, and lasted 84 days, 1 hour and 16 minutes. A total of 6,051 astronaut-utilization hours were tallied by Skylab 4 astronauts performing scientific experiments in the areas of medical activities, solar observations, Earth resources, observation of the Comet Kohoutek and other experiments.

The manned Skylab missions were officially designated Skylab 2, 3, and 4. Mis-communication about the numbering resulted in the mission emblems reading Skylab I, Skylab II, and Skylab 3 respectively.

Skylab 4 was the last Skylab mission.

The crew arrived on Skylab to find that they had company up there – three figures dressed in flight suits. Upon closer inspection, they found their companions were three dummies, complete with Skylab 4 mission patches and name tags which had been left there by Al Bean, Jack Lousma, and Owen Garriott at the end of Skylab 3.

Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of 169,950 pounds (77 t). Three manned missions to the station, conducted between 1973 and 1974 using the Apollo Command/Service Module (CSM) atop the smaller Saturn IB, each delivered a three-astronaut crew. On the third mission, an additional Apollo / Saturn IB stood by, ready for launch if needed to rescue the crew in orbit.

Skylab included an Apollo Telescope Mount (a multi-spectral solar observatory), Multiple Docking Adapter with two docking ports, Airlock Module with EVA hatches, and the Orbital Workshop, the main habitable volume of the station. Power came from solar arrays, as well as fuel cells in the docked Apollo CSM. The rear of the station included a large waste tank, propellant tanks for maneuvering jets, and a heat radiator.