Moncassin is a surname of French origin. Notable people with that name include:
Cathy Moncassin (born/ 1977). French/ cyclist Frédéric Moncassin (born 1968), French cyclist Henri Raphaël Moncassin (1883-1958), French sculptor
See also Leyritz-Moncassin, a commune in the Lot-et-Garonne department in south-western France Moncassin, a commune in the Gers department in southwestern France