The Foxtrot class was the NATO reporting name of a class of diesel-electric patrol submarines that were built in the Soviet Union. The Soviet designation of this class was Project 641. The Foxtrot class was designed to replace the earlier Zulu class, which suffered from structural weaknesses and harmonic vibration problems that limited its operational depth and submerged speed. The first Foxtrot keel was laid down in 1957 and commissioned in 1958 and the last was completed in 1983. A total of 58 were built for the Soviet Navy at the Sudomekh division of the Admiralty Shipyard, Saint Petersburg. Additional hulls were built for other countries.

The Soviet Navy's Project 611 were one of the first Soviet post-Second-World-War attack submarines. They were similarly capable to the American GUPPY fleet-boat conversions. They were a contemporary of the Whiskey-class submarines and shared a similar sonar arrangement. Like most conventional submarines designed 1946–1960, their design was influenced by the German World War II Type XXI U-boat.