Cybister ('kybistētēr' = diver, tumbler), is a genus of beetle in family Dytiscidae. They are found in much of the world, including all continents except Antarctica. As of 2021 there are 96 species and 9 additional subspecies among four subgenera in the genus.
Adult Cybister have broad hind legs with unequal tarsal claws (the inner claw being smaller and sometimes absent) and a fringe on the outer margin of the tarsus. They range in length from 13 mm (C. parvus from Brazil) to 43 mm (C. bimaculatus from the Afrotropics). Adult males of the North American species have several ridges on the coxae of the hind legs, forming a stridulatory device.
Larvae have a frontal tooth on the head and lack cerci. North American species can grow up to 80 mm long.
Cybister live in lentic (still fresh water) habitats that have vegetation.
Like other diving beetles, Cybister are predatory. Larvae of C. japonicus prey on inse