The Great Horned Owls (Bubo virginianus) of the Rocky Mountains were last comprehensively reviewed by Oberholser in 1904, who resurrected the name B. v. occidentalis. With minor modifications, this has been followed to date. With the suppression of occidentalis, which proved to be a synonym of subarcticus (Stone 1897 Am. Nat. 31:236; Dickerman 1991 Auk 108:964–965), the southern Rocky Mountain population, south of the Snake River in Idaho, was left without a name. Canonical discriminant analysis of 14 color and pattern characters provided 100% separation of the southern Rocky Mountain population nesting in higher elevation pinyon/oak/pine associations from those nesting at low elevations in Arizona and New Mexico (B. v. pallescens) and from the northern Rocky Mountain population north of the Snake River (B. v. lagophonus). Pair-wise comparisons showed that the mean vectors from each of the three populations were significantly different from each other (P < 0.001). We propose that the Great Horned Owls of the southern Rocky Mountains south of the Snake River of Idaho may now be known as Bubo virginianus pinorum, a new subspecies.