Congriscus megastomus is an eel in the family Congridae (conger/garden eels). It was described by Albert Günther in 1877, originally under the genus Congromuraena. It is a marine, temperate-water dwelling eel which is known from Japan and the Kyushu-Palau Ridge, in the northwestern Pacific Ocean. It inhabits reefs. Males can reach a maximum total length of 40 centimetres.