The first known fossil mecysmaucheniid spider, Archaemecys arcantiensis n. gen., n. sp., is described, from Lower Cretaceous (Upper Albian) amber of Charente-Maritime, France. This is the first fossil spider to be formally described from French Cretaceous amber and extends the geological record of Mecysmaucheniidae back into the Cretaceous, the family having previously been known only from the Recent. The fossil differs from other Mecysmaucheniidae in having four, rather than two spinnerets, so it can be considered plesiomorphic with respect to modern members of the family in this character. The amber of the Archingeay-Les Nouillers area is uniquely considered to have a largely preserved litter fauna and our specimen corroborates this hypothesis. Archaeidae, and now their sister group the Mecysmaucheniidae, have been found as fossils solely in the northern hemisphere, yet their Recent distributions are entirely southern hemisphere (Gondwanan). The find suggests a former pancontinental distribution of Mecysmaucheniidae.