Resumo. A new Butia (Becc.) Becc. (Arecaceae): Butia witeckii K. Soares & S. Longhi, native of the central region of Rio Grande do Sul - Brazil is described and illustrated. The species is related to Butia yatay (Mart.) Becc. and Butia paraguayensis (Barb. Rodr.) L.H.Bailey, differing from these two species by the size and weight of the fruit (3.6-5.6x3.0-4.1 cm with 23.61-43.05 grams); size, weight and shape of the endocarp/pyrene (2.8- 3.5x1.6-2.3 cm with 3.43-10.11 grams, possessing three longitudinal corners and almost always having a pyramidal shape near the germination pore), and by the number of pinnae (leaflets) on each side of rachis (43-61 pinnae). Differs from the latter species also by the length of the expanded portion of the peduncular bract (50-85 cm), by the legth of the inflorescence rachis (49-63 cm) and by the height of thetree (3.0-6.1 meters).