First record of Najas marina (Hydrocharitaceae) for Montana and an update on the North American distribution

Three recent collections of Najas marina (spiny water-nymph) from Missoula County, Montana are documented and illustrated. These collections are the first records for Montana and for the Pacific Northwest region. The occurrence of N. marina in Montana reflects a significant northward expansion of this species in the Mountain West. The North American distribution of this species is also updated.