The K-33 was a Soviet nuclear-powered Project 658 class submarine (NATO reporting name "Hotel II"). She belonged to the Soviet Northern Fleet and carried the identification number 921. In 1977, she was renamed K-54. K-33 was built at Factory No. 902 in Severodvinsk, Soviet Union, as a Hotel I class submarine, launched on 6 August 1960 and was commissioned on 5 July 1961. In 1964 the K-33 was repaired and modernized into "658M"-standard (Hotel II), by installing a new missile complex giving her capability to fire missiles while submerged. She was decommissioned in 1990.