A new mantispid genus and species Symphrasites eocenicus gen. sp. nov. is described from the Middle Eocene of the Messel Pit fossil site, Germany. It has been placed, with confidence, in the subfamily Symphrasinae, the fossils of which were previously unknown. A review of the known fossil species of Mantispidae is provided, and their systematic placements are discussed. Liassochrysa stigmaticaAnsorge & Schlüter, 1990 is assigned to Mantispidae, and therefore Liassochrysidae is a new synonym of Mantispidae; a second, more complete specimen of Mesomantispa sibiricaMakarkin, 1997 is described from the Early Cretaceous Baissa locality, Russia; MantispidipteraGrimaldi, 2000 is excluded from the family; Vectispa Lambkin, 1986 is referred to subfamily Mantispinae; and the assignment of WhalferaEngel, 2004 to Rhachiberothidae is validated. The origin and palaeobiogeography of the mantispids are briefly discussed: the concept of ousted relicts – which assumes that former widely distributed taxa were replaced with groups originating in the tropics – is assumed to best explain the present distribution of the family. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 701–716.