The Artemisia subgenus Tridentatae (Asteraceae-Asteroideae-Anthemideae-Artemisiinae) comprises 13 species, including 12 subspecies, of shrubs endemic to western North America. This monograph discusses morphology and anatomy, ploidy levels, phytogeography, and phylogeny. Full synonymies and descriptions are provided for all taxa, as well as a key, specimen citations, illustrations, and maps.