Cygnus is an expendable American uncrewed cargo spacecraft developed for International Space Station (ISS) resupply missions. It was originally built by Orbital Sciences Corporation with financial support from NASA under the Commercial Orbital Transportation Services (COTS) program. The spacecraft consists of a pressurized cargo module—based largely on the Multi-Purpose Logistics Module and built by Thales Alenia Space—paired with a service module derived from Orbital's GEOStar, a satellite bus. Following a successful demonstration flight in 2013, Orbital was awarded a Commercial Resupply Services (CRS) contract.

Over time, Cygnus has been upgraded to increase its size and capabilities. The Enhanced Cygnus variant debuted in 2015, and the further enlarged Cygnus XL entered service in 2025. Features added over time include reboost capability to raise the ISS orbit, the ability to support late cargo loading shortly before launch, and the option to conduct secondary missions after undocking. Each mission ends with a controlled destructive reentry, which also provides a means of disposing of waste generated aboard the station. Alongside Cygnus, other ISS resupply spacecraft have included the Russian Progress, the European Automated Transfer Vehicle, the Japanese H-II Transfer Vehicle, and the American SpaceX Dragon.

Cygnus is typically launched on its parent company’s Antares rocket from the Wallops Flight Facility in Virginia, but it can also fly aboard other launch vehicles. After an Antares failure destroyed Cygnus CRS Flight 3 and damaged Wallops in 2014, two subsequent missions launched on Atlas V rockets in 2015 and 2016. More recently, Cygnus missions have been launched on Falcon 9 rockets in 2024 and 2025, with another planned for 2026, under arrangements with CRS competitor SpaceX. The name Cygnus derives from the Greek word for swan and refers to the constellation.

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