In the present work the description and botanical classification of Acacia ibipocayensis Marchiori, new species for science and belonging to the subgenus Acacia Vassal, is made. It is a small shrub of yellow flowers in lonely axillary chapters by knot, and with composite leaves bipinadas provided with a pair of great spines stipulated in the insertion with the stem. The species in question was found in rocky canyons of the Ibirocai River, in the municipality of Alegrete, RS, the only natural occurrence site of the species known to date.
