The Quebec 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 A615.

Quebec-class submarines were fitted with two regular diesel engines and a third, closed-cycle diesel engine, which used liquid oxygen to provide air-independent propulsion while the submarine was submerged.

The Quebec class had a streamlined conning tower with a fixed snorkel housing at the rear end. They were armed with four torpedo tubes in the bow, for which no reloads were carried, and earlier boats also had a twin 25 mm anti-aircraft gun faired into the forward end of the tower, making them some of the last submarines to be constructed with deck guns.

The Quebec-class was plagued with problems caused by liquid oxygen evaporation. Their endurance was limited to 10 days due to continuous evaporation of the oxygen and lack of a re-liquefaction system, and the propulsion system led to several serious incidents. In 1957 two submarines were lost due to accidents caused by the oxygen system. M-256 suffered a fire off Tallinn in the Baltic, which led to the loss of 35 men, while M-351 sank in the Black Sea with no casualties. Other incidents caused oxygen-fueled flames to burst out from the boats, which led to their crews to nickname them zazhigalka ("lighters") or Zippos after the well-known cigarette lighter.

Submarine M-260 laid down 14 February 1954 at the Shipyard No.196, Leningrad (yard No.669), launched 21 May 1955, commissioned 31 July 1956 and was assigned to the Black Sea Fleet.

Submarine M-260 was decommissioned and excluded from the lists of the Black Sea Fleet 16 January 1970 and scrapped.