Cerion nanus is a species of medium-sized air-breathing land snail, a terrestrial pulmonate gastropod in the family Cerionidae.

eEcology== This species is endemic to the island of Little Cayman, Cayman Islands in the Caribbean Sea,[3] where it is found among Evolvulus arbuscula and E. squamosum plants,[4] which grow in this coastal dry limestone shrub.

Shells were found in 1975 at three sites, encompassing a total area of 35,000 m2 surrounding the North Shore Track.

It is sympatric throughout its range with Cerion pannosum, a species with a much larger distribution and shell-size, which has probably ecologically replaced C. nanus.

Currently several small populations exist along the Spot Bay Road in numbers far larger than originally suspected.