Rapana venosa (Valenciennes 1846) (Gastropoda: Muricidae), a mollusk native to Eastern Asia, is reported for the first time in Argentine waters in the north of Bahia Samborombon. During a routine bottom sampling, a female specimen of 97.1 and 76.3 mm shell length and width, respectively, and egg capsules were found approximately on 35.3øS -56.4øW in 13 m of water. The possible way of entrance is discussed. The finding of egg capsules permits the supposition that the introduced population is sexually mature and actively breeding. The presence of banks of mussels (Mytilus edulis platensis) and oysters (Ostrea puelchana), probable prey, together with the occurrence of the egg capsules point out that the development of R. venosa in Argentina could be ecologically and economically important.