Soyuz 4 was launched on 14 January 1969, carrying cosmonaut Vladimir Shatalov on his first flight. The aim of the mission was to dock with Soyuz 5, transfer two crew members from that spacecraft, and return to Earth. The previous Soyuz flight was also a docking attempt but failed for various reasons.

Soyuz 5 was a Soyuz mission using the Soyuz 7K-OK spacecraft launched by the Soviet Union on 15 January 1969, which docked with Soyuz 4 in orbit. It was the first docking of two crewed spacecraft of any nation, and the first transfer of crew from one space vehicle to another of any nation, the only time a transfer was accomplished with a space walk – two months before the United States Apollo 9 mission performed the first internal crew transfer.