A new early Eocene bat species is described from the Paris Basin locality of Pourcy (Marne), which is thought to represent either MP7 (early Ypresian; earliest Eocene) or MP8+9 (middle Ypresian; later early Eocene) in the European Paleogene mammal chronostratigraphic scale. It is the first bat described from the Pourcy locality, and one of the world’s oldest chiropterans. The new bat shares a number of archaic dental features found in other early bats, but also exhibits several traits that appear derived and suggest referral to the family Onychonycteridae. Onychonycterids are restricted to the Ypresian of France, Belgium, England, and the USA, and include the most skeletally primitive of bats. Onychonycterids lived alongside bats that exhibit adaptations for more advanced flight capabilities but which had dentitions that were somewhat more similar to those of ancestral placental mammals. The new bat species from Pourcy, together with other Ypresian chiropterans, illustrates the mosaic nature of bat evolution in the early Eocene.