This is the first paper on Canadian Cretaceous chalcidoid fossils of the families Mymaridae, Trichogrammatidae, and Tetracampidae, based on 54 specimens representing 12 species from Manitoba and Alberta. Four new subfamilies are proposed, Triadomerinae (Mymaridae), Baeomorphinae, Distylopinae, and Bouceklytinae (Tetracampidae). Descriptions and remarks are given forArchaeromma nearctican. gen., n. sp.;A.minutissima(Brues) (Mymaromminae);Triadomerus bulbosusn. gen., n. sp.;Carpenteriana tumidan. gen., n. sp.;Protooctonus masnerin. gen., n. sp. (Mymaridae);Enneagmus pristinusn. gen., n. sp. (Trichogrammatidae);Distylopus bisegmentusn. gen., n. sp.;Baeomorpha distinctan. gen., n. sp.,B.dubitataBrues (transferred from Scelionidae, Prototrupoidea),B.elongatan. sp.,B.ovatatan. sp. andBouceklytus arcuodensn. gen., n. sp. (Tetracampidae). A list of all previously known fossil Chalcidoidea is provided. A table of primitive and specialized conditions of characters studied is given. The possible lines of phylogeny of families and genera of these fossils are discussed. Keys to the pertinent families and subfamilies and to the fossil species ofBaeomorphaare provided. Photomicrographs of species treated are included.