Recent collecting in fossiliferous deposits at Lac des Bois, Northwest Territories, Canada, has produced the first record of acanthomorph fishes from the locality. Two specimens of acanthomorph, each representing a different taxon, were among the fishes collected. One of these is complete and well preserved; we here describe and name this fish, Boreiohydrias dayi, gen. et sp. nov. This fish is a polymixiiform, but it cannot be placed in any previously named family and we here give it a new family, Boreiohydriidae. The second acanthomorph is fragmentary; we describe it but do not formally name it. The relationships of early acanthomorph fishes are not easily determined, and still need much study, as do their living relatives. These two Turonian fishes are early members of the Acanthomorpha, which is first represented in the early Cenomanian in the Western Interior Seaway.