We present a taxonomic overview of the species of Oligoryzomys from the Brazilian Cerrado. We recognize seven species, including two described herein, making Oligoryzomys one of the most diverse mammalian genera of the Cerrado morphoclimatic domain. Oligoryzomys chacoensis occurs in the Cerrado and Chaco morphoclimatic domains. Oligoryzomys flavescens is distributed mainly in the Atlantic Forest of Brazil and the Pampas region of Argentina and Uruguay, but is also found in gallery forest in the Cerrado of Brazil near the border of the Atlantic Forest. Oligoryzomys stramineus and O. fornesi occur in the Cerrado and Caatinga morphoclimatic domains. Oligoryzomys nigripes is found in the Atlantic Forest and in the Southern portion of the Cerrado. The two new species are endemic to the Cerrado, and one of them is found only in “campo rupestre” vegetation. Oligoryzomys eliurus and O. delticola are placed tentatively as junior synonyms of O. nigripes. Oligoryzomys fornesi is recognized as a distinct species from O. microtis.
