Planorbis is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod molluscs in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.

Planorbis shells are flat-coiled and sinistral.

This genus has a worldwide distribution. It is known from the Jurassic to the Recent periods.

Species in the genus Planorbis have long been used in the aquarium trade, with references going back as far as 1921.