Soyuz 31 was a 1978 Soviet crewed space flight to the Salyut 6 space station. It was the seventh mission to and sixth successful docking at the orbiting facility. The Soyuz 31 crew were the second to visit the long-duration Soyuz 29 resident crew.

Salyut 6, DOS-5, was a Soviet orbital space station, the eighth station of the Salyut programme. It was launched on 29 September 1977 by a Proton rocket. Salyut 6 was the first space station to receive large numbers of crewed and uncrewed spacecraft for human habitation, crew transfer, international participation and resupply, establishing precedents for station life and operations which were enhanced on Mir and the International Space Station.