Late Cretaceous marine turtles are rare in Canada, but specimens are known from three formations: Toxochelys latiremis Cope and Protostega sp. from the Pierre Shale, Pembina Member (lower Campanian); Lophochelys niobrarae Zangerl and Chelonioidea genus indet. from the Bearpaw Formation (upper Campanian); Protostegidae genus indet. and one other taxon from the Niobrara Formation (Coniacian).The Canadian records of the listed taxa constitute the northernmost limits of their known range and may represent their northern limits in the Cretaceous inland sea. Taxonomic diversity and relative abundance of turtles in the Canadian samples are significantly less than in comparable faunas to the south. Cool marine climates may have excluded local nesting and discouraged migrations into northern areas.