Ectemnius trifasciatus is a solitary wasp in the family Crabronidae, originally described by Thomas Say in 1824 under the basionym Crabro trifasciatus. As a member of the genus Ectemnius, it is part of a group of digger wasps known to nest in wood and provision their young with paralyzed flies. The species is recorded from North America, with specific observations from Alberta, Canada.