The world species of the genus Sinophorus Foerster (Ichneumonidae: Porizontinae) are revised. One hundred and three species and 5 subspecies are recognized. Eighty-one species and 5 subspecies are described as new. Twenty-three species are redescribed. Two lectotype designations were made: pleuralis (Thomson), quettaensis (Cameron) (=nitidus (Brischke)). Three species were removed from synonymy and recognized as valid species: canadensis (Viereck) and teratis (Weed) from validus (Cresson); renominatus (Morley) from turionus (Ratzeburg). One new combination was created: relativus (Viereck) from Campoplex. Eight names were placed in synonymy: albicinctus (Viereck), quettaensis (Cameron) and tegularis (Thomson) = nitidus (Brischke); alkae (Ellinger and Sachtleben) and rufifemur (Thomson) = turionus (Ratzeburg); ornatus (Gregor) and juniperinus alpinator Aubert = juniperinus (Holmgren); pineticola (Thomson) = xanthostomus (Gravenhorst).
The limits of the genus Sinophorus are defined. Keys to the world species (females and males) of Sinophorus are presented. Zoogeography, phylogeny and biology of Sinophorus are discussed. Taxonomic characters used to separate species of Sinophorus are illustrated by means of the line drawings and scanning electron micrography and distribution maps are provided for each species unless otherwise indicated.