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This is an accepted article with a DOI pre-assigned that is not yet published.Largely thanks to their penchant for blood-feeding, leeches have been exploited by humans for millennia. In spite of their relevance as medical tools, model organisms, livestock pests, and pathogen vectors, the higher-level phylogenetic relationships of Hirudinea (Annelida: Clitellata) are not well-understood. Furthermore, leech taxonomy is plagued by uncertainty, and increasing evidence suggests that many accepted classifications do not agree with evolutionary relationships. Here, we present the most comprehensive phylogenetic study of Hirudinea to date using a dataset composed of one third of described leech species (Hirudinida), one third of described crayfish worms (Branchiobdellida), and half of described Acanthobdellida. We produce a well-supported tree, discuss its implications for hirudinology broadly, and revisit the question of whether proboscis-bearing leeches (previously united under the order “Rhynchobdellida”) are monophyletic. Guided by our results, we rectify multiple major, outstanding issues in leech classification by redefining certain higher taxa and erecting the new family Hirudinaridae.