The Kilo class is the NATO reporting name for a military diesel-electric submarine that is made in Russia. The original version of the vessels were designated Project 877 Paltus in Russia. There is also a more advanced version, designated as Improved Kilo in the west, and Project 636 Varshavyanka in Russia.

The boats are mainly intended for anti-shipping and anti-submarine operations in relatively shallow waters. Original Project 877 boats are equipped with Rubikon MGK-400 sonar system, which includes a mine detection and avoidance sonar MG-519 Arfa. Newer Project 636 boats are equipped with improved MGK-400EM, with MG-519 Afra also upgraded to MG-519EM. The improved sonar systems have reduced the number of operators needed by sharing the same console via automation. Project 636, sometimes called "The Black Hole" by the US Navy for its uncanny ability to "disappear", is thought to be one of the quietest diesel-electric submarine classes in the world.

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