In this paper we describe and illustrate Sinningia ramboi (Gesneriaceae), a new species occurring on rocky outcrops in the upper parts of the canyons cutting the plateau of high altitude grasslands in Rio Grande do Sul, Brazil. This new species bears some similarity to S. polyantha, S. nivalis, and S. douglasii, but is readily distinguished by opposite leaves and a much shorter main axis of the inflorescence. Ecological and distributional data, as well as a key to distinguish these related species, are also presented.