Bothragonus swanii, the rockhead, deep-pitted poacher or deep-pitted sea-poacher, is a fish in the poacher family, Agonidae. It was described by Franz Steindachner in 1876, originally in the genus Hypsagonus. It is found in the eastern Pacific Ocean from Alaska to Carmel Bay, California down to depths of 18 metres. It can also inhabit the intertidal zone. Males can reach a maximum total length of 8.9 centimetres.