Fossil mayfly larvae (cf. Heptageniidae) are reported for the first time in the Cretaceous of Canada. The new fossils come from the latest Campanian part of the Wapiti Formation, which crops out in west-central Alberta, near the British Columbia border. These sediments represent mixed lentic and lotic fluvial environments consistent with modern heptageniid ecology. This discovery helps fill a significant temporal gap in heptageniid evolution between the Eocene and their earliest appearance in the Turonian.