Taxonomy of the genus Huperzia (Lycopodiaceae) in western North America and Europe was studied using morphological characters. Delimitations of species were redefined after examining the morphology of the H. selago lectotype and other type specimens in the genus. Two new species were named, H. acicularis Björk from North America and Eurasia, and one species apparently endemic to Europe, H. europaea Björk. Huperzia occidentalis and H. porophylla were found to be conspecific with the Macaronesian endemic H. suberecta, which is the oldest name of the three. Additionally, H. suberecta was found to be common and widespread in the northern hemisphere; it and H. europaea are frequently confused with H. selago. A key to European and western North American Huperzia is presented.