The new species Oritrophium acerosum (Compositae, Astereae) is described from the páramo de Patococha at the border between the provinces of Azuay and Morona-Santiago, southern Ecuador. Among other features, the species is characterized by its reduced size, rosettes composed of 20–35 leaves much shorter than the scape, and linear, strongly revolute leaves with a glabrous adaxial surface, and pseudopetioles longer than the lamina. A taxonomic discussion of similar species is provided, as well as detailed pictures of living plants and a dichotomous key to the species of the genus in Ecuador.
