This contribution provides the first integrative revision of the Siphonaria species described and reported from southern South America, by combining information on shell morphology, distal portion of the genital system, radula, molecular data and living animal. More than 200 lots, from all along the Uruguayan, Argentinean and southern Chilean coasts, including the Malvinas (Falkland) Islands and South Georgia, were studied. Among the nine nominal species listed for this area, only the presence of Siphonaria lessonii Blainville, 1827 and S. lateralisGould, 1846 could be confirmed. The intraspecific variability of these two species along their distributional ranges is examined. Siphonaria magellanicaPhilippi, 1855 and S. antarcticaGould, 1852 are regarded as probable synonyms of S. lessonii. The Magellanic records of S. tristensis are reassigned to S. lessonii and those of S. macgillivrayi to S. fuegiensis n. sp. The similarity of S. redimiculumReeve, 1856, S. laeviusculaSowerby, 1835 and S. lineolataSowerby, 1835 to the three species confirmed in the studied area is discussed. The Chilean S. laevisPhilippi, 1846 is considered a nomen dubium. All available types are figured and a lectotype is designated for S. redimiculum.