The Arctomys Formation is a stratigraphic unit of late Middle Cambrian age. It is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Arctomys Peak near Mount Erasmus in Banff National Park by Charles Doolittle Walcott in 1920. Outcrops of the Arctomys can be seen in Banff and Jasper National Parks.