In the early years of his research on the native trouts of western North America, Behnke (1960, 1966, 1979) observed consistent differences in certain meristic characters between the cutthroat trout of the Humboldt River drainage and those from the Truckee, Carson, and Walker river drainages of the Lahontan Basin, and proposed that the Humboldt trout be recognized as a distinct subspecies. He coined the subspecies name humboldtensis, but a formal description was never published. Here we again present the early evidence for subspecific distinction of the Humboldt drainage cutthroat trout, and add more recent findings from the fields of population genetics and Pleistocene and recent zoogeography that support this interpretation. Based on this evidence, we offer a formal description of the cutthroat subspecies Oncorhynchus clarkii humboldtensis and map its likely historical distribution. Available meristic and zoogeographic evidence indicates that the native trouts of the upper Quinn River, Nevada and Oregon and the Coyote Basin of Oregon should be included with humboldtensis as well.