Potamilus alatus (Pink Heelsplitter) is a rare freshwater mussel in the Ottawa River drainage (Ontario/Québec, Canada), at the northeastern limit of its distribution. There are few historical records, and one old specimen from an uncertain locality. The discovery of the Pink Heelsplitter in the Ottawa River drainage dates from 1863. A few specimens were reported up to 1901, but it was August 2001 before another specimen was found in the Ottawa River, as an empty shell at Upper Duck Island, near Ottawa. From 2001 to 2005, the authors found this freshwater mussel at four localities along the Ottawa River, and two in the tributary South Nation River. Records include 4 living specimens and 12 empty shells, of which 8 were in fresh condition. The Pink Heelsplitter seems to persist sparsely in the Ottawa River, but it may have been extirpated from one of its tributaries (South Nation River) before its discovery due to mortality associated with Dreissena polymorpha (Zebra Mussel).