Gemini 8 was the first crewed spacecraft to dock with another spacecraft in orbit, connecting with an uncrewed Agena target vehicle on March 16, 1966.
NASA astronauts Neil Armstrong and David Scott performed the docking during the mission. The achievement demonstrated a key technique needed for Apollo lunar missions, where crews would have to rendezvous and dock in space.
Soon after docking, the joined vehicles began spinning rapidly because of a stuck thruster. Armstrong undocked Gemini 8 and used the reentry-control system to stop the rotation, but this consumed much of the spacecraft’s control fuel.
The mission ended early with an emergency landing in the Pacific Ocean. Despite the shortened flight, its successful docking became a major milestone in human spaceflight.