Soyuz TMA-15 was a crewed spaceflight to the International Space Station. Part of the Soyuz programme, it transported three members of the Expedition 20 crew to the space station. TMA-15 was the 102nd crewed flight of a Soyuz spacecraft, since Soyuz 1 in 1967. The Soyuz spacecraft remain docked to the space station during Expedition 20 and Expedition 21 as an emergency escape vehicle. The mission marked the start of six-person crew operations on the ISS.

The Soyuz is a Soviet crewed spacecraft, developed to perform lunar missions with crew. This version called 7K will fly 4 times on the giant launcher N1, and several tens of times on Proton to fly over the Moon, which will be successful during the mission Zond 4. Soyuz will become the first spacecraft to transport living beings on the Moon during the flight of Zond 5, with two turtles. Thereafter, it is adapted to the low orbit and will fly on the Soyuz launcher to supply the Soviet Salyut and Mir stations, and the ISS.