A new species of polycotylid, Dolichorhynchops herschelensis, is described based on a well-preserved skeleton from the Upper Cretaceous (Campanian–Maastrichtian) Bearpaw Formation of Herschel, Saskatchewan. Its small size as an adult, the sharp rise in front of the parietal crest, and the straight ilium with narrow dorsal end are diagnostic features of this taxon. This is the first polycotylid plesiosaur described from the Bearpaw Formation, deposited during the critical period when polycotylids were disappearing from the Western Interior of North America.