Technical Abstract: Tamarix species (Tamaricaceae) invading natural and seminatural habitats in Argentina. The genus Tamarix includes species behaving as aggressive invaders in the USA, México and Australia. Previous studies report a variable number of species of this genus cultivated in Argentina as ornamentals,wind-break or for shadow, or growing spontaneously. This work makes clear some confusion related to synonyms and confirms the presence of four species in our country: T. gallica, T. ram'osissima, T.chinensis and T. parviflora, the former three recorded colonizing natural and semi-natural habitats. A description of these species is given, together with a key for their identification, and information of their geographical distribution in Argentina, including maps showing the occurrence of established and invasive populations.