K-129 was a Project 629A diesel-electric-powered ballistic-missile submarine that served in the Pacific Fleet of the Soviet Navy–one of six Project 629 strategic ballistic-missile submarines assigned to the 15th Submarine Squadron based at Rybachiy Naval Base near Petropavlovsk, commanded by Rear Admiral Rudolf Golosov.

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).