The riffle minnow (Phenacobius catostomus) is a North American species of cyprinid freshwater fish. It inhabits riffles in warm streams of medium to large size, in the states of Alabama, Georgia, and Tennessee, above the Fall Line. Long and slender, it averages about 3.5 inches (8.9 cm) in length. The riffle minnow is olive on top, and white below.