Abstract
The genus Aongstroemia is here reported as new for Argentina and Uruguay, based on collections of A. gayana, formerly considered a Chile endemic. The species is described and illustrated, and its distribution depicted in a map. We also report A. filiformis as new for the southern cone of South America, based on a single collection from Contulmo, Chile. We provide a key for the identification of the species of Aongstroemia of Latin America.