Ligia is a genus of isopods, commonly known as rock lice or sea slaters.

[1] While they have gills and can exchange gas under water, they only do so when escaping terrestrial predators or being dislodged by wave action.

They are well adapted to rocky surfaces and avoid sand, which opens them to terrestrial predation and desiccation.

[2] It has been suggested that Ligia is more closely related to marine isopods than it is to true woodlice.

The males also tend to be larger but narrower, with the difference sometimes attributed to the female's brood pouch.