Diolcogaster is a genus of parasitoid wasps within the subfamily Microgastrinae of the family Braconidae. The genus is poorly studied, likely with multiple undescribed species. The type species is Diolcogaster melligaster <small>(Provancher, 1886)</small>, formerly Microgaster melligaster. Species in this genus parasitize lepidopterans and are geographically widespread. There are more than 140 described species in Diolcogaster found throughout the world.