Phainantha shuariorum (Melastomataceae) from sandstone mountains of the Cordillera del Cóndor region in southeastern Ecuador is described and illustrated; it is a disjunct species in a genus that is otherwise known only from the Guayana Shield region of northeastern South America. It resembles P. laxiflora and P. maguirei, with which it shares the climbing, twining habit, adventitious roots at the stem nodes, and leaves alternate by abortion of one leaf per pair, but from which it differs in the tri-nerved venation.