The Apollo–Soyuz Test Project, conducted in July 1975, was the first joint U.S.–Soviet space flight, as a symbol of the policy of détente that the two superpowers were pursuing at the time. It involved the docking of an Apollo Command/Service Module with the Soviet Soyuz. The unnumbered Apollo vehicle was a surplus from the terminated Apollo program and the last one to fly. This mission ceremoniously marked the end of the Space Race that had begun in 1957 with the Sputnik launch.
https://en.wikipedia.org/wiki/Apollo%E2%80%93Soyuz_Test_Project