K-219 was a Project 667A Navaga-class ballistic missile submarine of the Soviet Navy. It carried 16 R-27U liquid-fuel missiles powered by UDMH with nitrogen tetroxide (NTO). K-219 was involved in what has become one of the most controversial submarine incidents during the Cold War on Friday 3 October 1986. The 15-year-old vessel, which was on an otherwise routine Cold War nuclear deterrence patrol in the North Atlantic 1,090 kilometres (680 mi) northeast of Bermuda, suffered an explosion and fire in a missile tube. While underway a submerged seal in a missile hatch cover failed, allowing high-pressure seawater to enter the missile tube and owing to the pressure differential ruptured the missile fuel tanks, allowing the missile's liquid fuel to mix and ultimately combust. Though there was no official announcement, the Soviet Union claimed the leak was caused by a collision with the submarine USS Augusta. Although Augusta was operating within the area, both the United States Navy and the commander of K-219, Captain Second Rank Igor Britanov, deny that a collision took place.

The Yankee class, Soviet designations Project 667A Navaga (navaga) and Project 667AU Nalim (burbot) for the basic Yankee-I, were a family of nuclear-powered ballistic missile submarines built in the Soviet Union for the Soviet Navy. In total, 34 units were built: 24 in Severodvinsk for the Northern Fleet and the remaining 10 in Komsomolsk-on-Amur for the Pacific Fleet. Two Northern Fleet units were later transferred to the Pacific.