Cassegrain is a lunar impact crater that is located on the far side of the Moon, beyond the southeastern limb. It lies to the southeast of the larger crater Lebedev, and to the northeast of the comparably-sized Priestley. It is named after the inventor of the Cassegrain reflector, who was later identified as most likely the French priest Laurent Cassegrain. The designation was officially adopted by the International Astronomical Union in 1970.