Soyuz 16 (Russian: Союз 16, Union 16) was a 1974 manned test flight for a joint Soviet-US space flight which culminated in the Apollo-Soyuz mission in July 1975. The two-man Soviet crew tested a docking ring and other systems to be used in the joint flight.

The Soyuz 16 mission was the final rehearsal and first manned mission in a program which culminated in the Apollo-Soyuz (ASTP) mission seven months later. The Soviet Union and the United States of America, Cold War rivals, had signed several arms control treaties in the 1960s and 1970s, and had entered into a period of detente by the early 1970s. In 1972, a treaty was signed to participate in a joint manned space flight as a symbol of this detente.

Early concepts for a joint flight included docking a Soyuz craft to the American Skylab space station, or an Apollo vehicle docking with a Salyut space station. Once the Americans abandoned their Skylab station in 1974, the Apollo-Salyut concept seemed to be the logical choice, but since the Soviets had started to develop a universal docking adapter for the mission and feared having to publicly reveal details of their military-focused Salyut missions, the two powers opted to link a Soyuz spacecraft with an Apollo spacecraft.

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