The Leninets or L class were the second class of submarines to be built for the Soviet Navy. Twenty-five were built in four groups between 1931 and 1941. They were minelaying submarines and were based on the British L-class submarine, HMS L55, which was sunk during the British intervention in the Russian Civil War. Some experience from the previous Dekabrist-class submarines was also utilised. The boats were of the saddle tank type and mines were carried in two stern galleries as pioneered on the pre-war Russian submarine Krab (1912). These boats were considered successful by the Soviets. Groups 3 and 4 had more powerful engines and a higher top speed.

The Dekabrist class, also known as Series I, were the first class of submarines built for the Soviet Navy after the October Revolution of 1917. They were authorized in the Soviet Naval Shipbuilding Program of 1926, marking the revival of submarine design in Russia. They were authorized in the Soviet Naval Shipbuilding Program of 1926, and began their sea trials in 1930.