The first species of the small Afrotropical family Ammodesmidae discovered in central Africa (Democratic Republic of the Congo) belongs to the genus Ammodesmus Cook, 1896, which was hitherto known only from two species in western Africa. A key is given to incorporate A. congoensis sp. n., a species also showing an evident sex dimorphism: ♂ densely hirsute, ♀ with much longer and sparser tergal setae.