K-219 was a Project 667A Navaga-class ballistic missile submarine (NATO reporting name "Yankee I") of the Soviet Navy. She carried 16 (later 15) SS-N-6 liquid-fuel missiles powered by UDMH with IRFNA, equipped with an estimated 34 nuclear warheads. K-219 was involved in what has become one of the most controversial submarine incidents in the Cold War.