The paper describes a new species of the genus Thermochiton, T. papuaensis sp. nov., found in deep waters off Papua New Guinea. This species differs from T. undocostatus primarily in the dorsal scales, the marginal spicules, sculpture of the jugal area and the shape of the central teeth of radula. There are apparent similarities between the species of the genus Thermochiton, Connexochiton platynomenus, C. kaasi and Ischnochiton crassus. The last species is proposed to be transferred to Connexochiton. Owing to the friable, rusty brown deposits that densely cover the shell and girdle of both specimens of T. papuai, the latter probably lives in areas of high chemical activity.