Maddenia is an extinct genus of astrapothere, meridiungulate herbivore mammals characterised by its large tusks and the development of proboscis, endemic of South America. This genus was discovered in an outcrop near to the Lake Colhué Huapi in the place La Cantera, in the Chubut Province, in Argentina, in sediments corresponding to the Sarmiento Formation, that dates of the late Oligocene (Deseadan mammal age).