The genus Mitrephora (Annonaceae) comprises 47 species of small to medium-sized trees, growing in tropical lowland and submontane forests throughout Southeast Asia. The centers of diversity lie in Borneo, where there are 12 species, and the Philippines, where there are 11 species. The flowers are pendent and hermaphroditic, with two whorls of petals, of which the outer petals are larger. The inner petals are apically connivent over the reproductive structures, forming a partially enclosed pollination chamber with small apertures between the basal claws of the petals that enable entry by pollinators. A field study of the pollination ecology of M. heyneana in Sri Lanka (the first such study for the genus) revealed pollination by small nitidulid beetles, although it is possible that other species may be fly-pollinated. This monograph is the first comprehensive taxonomic revision of the genus. The work is based on a comprehensive study of comparative morphology and anatomy, including a survey of previously published work. Conservation assessments are provided for each species, according to current lUCN Red List categories and criteria. All species are mapped and many are illustrated with line drawings and/or photographs. Separate keys for flowering and fruiting material are included, as well as regional keys. Seven new species (M, amdjahii, M. endertii, M. kostermansii, M. multifolia, M. sorsogonensis, M. sundaica, and M. uniflora) and one new combination (M. macrocarpa) are proposed.