Sicyopus (Smilosicyopus) pentecost n. sp., a carnivorous freshwater goby, is described on the basis of nine specimens (five males, four females) collected from high gradient streams on the islands of Pentecost (Vanuatu) and Bélep (New Caledonia). This species differs from other species of the subgenus Smilosicyopus by a combination of characters that include more upper jaw teeth (21-26), less scales in lateral series (14-29), less scales in zigzag series (11-14), a greater length in second dorsal fin in female, and a shorter caudal peduncle.