The Mission was the Apollo-Soyuz Test Project
The Apollo-Soyuz Test Project was the first spaceflight that included two nations working together with their own national spacecraft. The Americans sent up an Apollo command module, while the Russians launched a Soyuz spacecraft.
"The Soyuz and Apollo spacecraft docked on July 17, 1975, in a demonstration of how well the rendezvous and docking systems of each spacecraft would work with each other. The combined crew of five people — three Americans, two Soviets — spent about two days in orbit working on experiments and conducting joint press conferences."