The Project 205 Moskit (mosquito) more commonly known by their NATO reporting name Osa, are a class of missile boats developed for the Soviet Navy in the late 1950s. Until 1962 this was classified as a large torpedo boat.

A missile boat or missile cutter is a small, fast warship armed with anti-ship missiles. Being smaller than other warships such as destroyers and frigates, missile boats are popular with nations interested in forming a navy at lower cost. They are similar in concept to the torpedo boats of World War II; in fact, the first missile boats were modified torpedo boats with the torpedo tubes replaced by missile tubes.