Project 629, also known by the NATO reporting name Golf, was a class of diesel-electric ballistic missile submarines that served in the Soviet Navy. All boats of this class had left Soviet service by 1990, and have since been disposed of. According to some sources, at least one Golf-class submarine was operated by China, to test new submarine-launched ballistic missiles (SLBMs).

A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.