Soyuz 5 (Russian: 5, Union 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.

The mission, flown by cosmonauts Boris Volynov, Aleksei Yeliseyev, and Yevgeny Khrunov, was also memorable for its dramatic re-entry. The craft's service module did not separate, so it entered the atmosphere nose-first, leaving Volynov hanging by his restraining straps. As the craft aerobrake, the atmosphere burned through the module. But the craft righted itself before the escape hatch was burned through. Then, the parachute lines tangled and the landing rockets failed, resulting in a hard landing that broke Volynov's teeth.

Soyuz 4 (Russian: Союз 4, Union 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 (Soyuz 3) was also a docking attempt but failed for various reasons.

The radio call sign of the crew was Amur, while Soyuz 5 was Baikal. This referred to the trans-Siberian railway project called the Baikal-Amur Mainline, which was in development at the time.