Eucosma is one of the largest genera in the Tortricidae, with more than 230 described species. It achieves its greatest species richness in the Nearctic, where members of the genus can be found in nearly every habitat, from the dunes of the Gulf Coast to the barren summits of the Rocky Mountains. This volume is the first comprehensive treatment of North American Eucosma to be published in more than 90 years. One hundred and thirty-three species are reviewed from the contiguous United States and Canada. Nine new species are described, nine new synonymies are proposed, 21 lectotypes are designated, and several unresolved species complexes are discussed. Diagnostic morphological features useful in species identification are emphasized and illustrated with 450 color adult images and 629 detailed genitalia drawings.