К-3 was a project 627 "Кит" submarine of the Soviet Navy's Northern Fleet, the first nuclear submarine of the Soviet Union. The vessel was prototyped in wood, with each of five segments scattered between five different locations about Leningrad, including the Astoria Hotel. She was built in Molotovsk, launched on 9 August 1957, commissioned in July 1958, and homeported at Zapadnaya Litsa on the Kola Peninsula. K-3 was designed by Vladimir Peregoudov. Her initial captain was Leonid Osipenko, and the executive officer was Lev Zhiltsov, who had the important task of assembling the first crew.

The Northern Fleet is the fleet of the Russian Navy in the Arctic.