A new genus of Gerridae (Insecta, Hemiptera, Heteroptera) in the subfamily Trepobatinae, Telmatome tropsis gen. nov., with a single included species, T. fredyi sp. nov., is described from the Colombian Pacific region. Representatives of the new genus were collected in mangrove lagoons of Buenaventura Bay, Valle del Cauca Department. The new genus can be diagnosed by the relative proportions of the antennomeres, the shape of the male fore tarsus, and by the black markings on the head, thorax and abdomen.