ApolloSoyuz was the first crewed international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo spacecraft docked with a Soviet Union Soyuz capsule. The project, and its memorable handshake in space, was a symbol of dtente between the two superpowers during the Cold War, and it is generally considered to mark the end of the Space Race, which had begun in 1957 with the Soviet Union's launch of Sputnik 1.The mission was officially known as the ApolloSoyuz Test Project (ASTP; Russian: « « (), romanized: Eksperimentalniy polyot SoyuzApollon (EPAS), lit.'Experimental flight Soyuz-Apollo', and commonly referred to in the Soviet Union as SoyuzApollo; the Soviets officially designated the mission as Soyuz 19). The unnumbered American vehicle was left over from the canceled Apollo missions, and was the last Apollo module to fly.

The three American astronauts, Thomas P. Stafford, Vance D. Brand, and Deke Slayton, and two Soviet cosmonauts, Alexei Leonov and Valeri Kubasov, performed both joint and separate scientific experiments, including an arranged eclipse of the Sun by the Apollo module to allow instruments on the Soyuz to take photographs of the solar corona. The pre-flight work provided useful engineering experience for later joint AmericanRussian space flights, such as the ShuttleMir program and the International Space Station.

ApolloSoyuz was the last crewed United States spaceflight for nearly six years until the first launch of the Space Shuttle on 12 April 1981, and the last crewed United States spaceflight in a space capsule until Crew Dragon Demo-2 on May 30th, 2020.

The Space Race was a 20th-century competition between two Cold War adversaries, the Soviet Union and the United States, to achieve superior spaceflight capability. It had its origins in the ballistic missile-based nuclear arms race between the two nations following World War II. The technological advantage demonstrated by spaceflight achievement was seen as necessary for national security, and became part of the symbolism and ideology of the time. The Space Race brought pioneering launches of artificial satellites, robotic space probes to the Moon, Venus, and Mars, and human spaceflight in low Earth orbit and ultimately to the Moon.The competition began in earnest on August 2, 1955, when the Soviet Union responded to the American announcement four days earlier of intent to launch artificial satellites for the International Geophysical Year, by declaring they would also launch a satellite "in the near future". The developments in ballistic missile capabilities made it possible to take the competition between the two states into space. This competition gained public attention with the "Sputnik shock", when the USSR achieved the first successful artificial satellite launch on October 4, 1957 of Sputnik 1, and subsequently when the USSR sent the first human to space with the orbital flight of Yuri Gagarin on April 12, 1961. The USSR demonstrated an early lead in the race with these and other firsts over the next few years, reaching the Moon for the first time with the Luna programme by employing robotic missions.

After US president John F. Kennedy raised the stakes by setting a goal of "landing a man on the Moon and returning him safely to the Earth", both countries worked on developing super heavy-lift launch vehicles, with the US successfully deploying the Saturn V, which was large enough to send a three-person orbiter and two-person lander to the Moon. Kennedy's Moon landing goal was achieved in July 1969, with the flight of Apollo 11, a singular achievement considered by the Americans as overshadowing any combination of Soviet achievements that have been made. However, such an opinion is generally contentious, with others attributing the first man in space as being a much larger achievement. The USSR pursued two crewed lunar programs, but did not succeed with their N1 rocket to launch and land on the Moon before the US, and eventually canceled it to concentrate on Salyut, the first space station programme, and the first time landings on Venus and on Mars. Meanwhile, the US landed five more Apollo crews on the Moon and continued exploration of other extraterrestrial bodies robotically.

A period of détente followed with the April 1972 agreement on a co-operative Apollo–Soyuz Test Project (ASTP), resulting in the July 1975 rendezvous in Earth orbit of a US astronaut crew with a Soviet cosmonaut crew and joint development of an international docking standard APAS-75. Being considered as the final act of the Space Race, the competition would only gradually be replaced with cooperation. The collapse of the Soviet Union eventually allowed the US and the newly founded Russian Federation to end their Cold War competition also in space, by agreeing in 1993 on the Shuttle–Mir and International Space Station programs.