Prostanthera monticola, commonly known as Buffalo mintbush, is a shrub which is native to south-eastern Australia. It has a spreading habit, growing to between 0.3 and 2 metres high. The leaves are 15 to 50 mm long and 5 to 13 mm wide. Flowers appear in the leaf axils in summer. They are about 18 to 20 mm long and pale blue-green or grey-green with purple veining. The species was formally described in 1984 based on plant material collected at Crystal Brook Falls, Mount Buffalo in Victoria. Prior to 1984, plants had been identified as Prostanthera walteri.