A comprehensive systematic monograph is presented for the genus Operculina Silva Manso (Convolvulaceae). Formerly included in tribe Merremieae D. F. Austin, now incertae sedis, recent systematic studies have clarified the phylogenetic relationships for Operculina and unequivocally demonstrated that it is monophyletic as currently circumscribed and that the unique operculate capsule is a synapomorphy for the genus. Other morphological characters useful for recognizing the genus are: large sepals forming a “pear-shaped” calyx that is broad at the base and tapers upward; calyx that is accrescent and persistent, often cupping the mature fruit; strongly spirally coiled anthers after dehiscence; and axial parts of the plant body (stems, petioles, peduncles, pedicels) that are often prominently winged. The current monograph accepts 13 species, including one variety and one purported hybrid; these taxa are distributed throughout the tropics globally. The hybrid is proposed to accommodate the extraordinary phenotypic variability and intermediacy among South Pacific populations of Operculina. The monograph provides detailed descriptions for all taxa, as well as an identification key, distribution maps, and summaries of ecology, phenology, vernacular names, and uses, with comments on synonymy, typification, variability, biology, and conservation, where appropriate. All names published or combined in Operculina (about 60 epithets) are accounted for as accepted names, synonyms, misapplied names, or uncertain names, or are excluded from the genus. New reductions to synonymy are proposed as follows: O. brownii Ooststr. becomes a synonym of O. codonantha (Benth.) Hallier f.; O. tansaensis Santapau & V. Patel becomes a synonym of O. ventricosa (Bertero) Peter. Lectotypes, neotypes, and epitypes are designated where necessary to stabilize names in current use. An index to numbered collections examined is provided to aid in specimen identification and herbarium curation.