The CANT Z.509 was a three-engine Italian floatplane developed from the Z.506A for use as a mailplane.
Designed as a larger and heavier version of the Z.506A, three aircraft were built in 1937 for Ala Littoria. The aircraft were for use on the airline's transatlantic postal service to South America. The aircraft was a twin-float seaplane powered by three Fiat A.80 R.C.41 radial engines.With the outbreak of World War II, development of the type was abandoned.