Tumidocarcinus is an extinct genus of large crabs in the family Tumidocarcinidae, containing the following species:
It is a host of the parasitic Kentrogonida barnacles.
This genus is known in the fossil record from the Eocene to the Miocene epoch. Most species of Tumidocarcinus are known from New Zealand and Australia, however, T. foersteri is known from the La Meseta Formation from Seymour Island, Antarctica.