Mesoleptus is a genus of parasitic wasp in the family Ichneumonidae with a wide geographic distribution.

[2] The antennae of its members are typically long, slender, and usually curved.

The head is short and narrow with oval, slightly protruding eyes.

[3] In 2008, Dr. Chris Williams at the National University of Ireland, Galway announced the discovery of what he believed to be a new species of Mesoleptus, for which he suggested the name Mesoleptus hibernica (for the ancient Latin name for Ireland) in an interview.

[7] 172 of the more than 200 species were described by Arnold Förster of Aachen, Germany.