The endemic Madagascan genus Tricompastes Cachan, 1952 (Hemiptera: Heteroptera: Pentatomidae: Pentatominae: Triplatygini), containing a single species-Tricompastes gigas Cachan, 1952, is redescribed and illustrated, including first descriptions of male and female genitalia. First exact localities of the species are provided. Lectotype of T. gigas is designated.