This paper explores the phonological status of the labial flap in Mambay, a language belonging to the Adamawa division of Niger-Congo. Until recently, little discussion of the speech sound known as the labial flap has been found in the literature. However, in a series of recent articles, Olson and Hajek have used cross-linguistic evidence to argue for the treatment of the labial flap as a basic speech sound; this has resulted in its recent inclusion in the International Phonetic Alphabet (IPA). The present study adds to the discussion by providing an example of a language in which the labial flap is profoundly phonologized. Its distribution in the phonology, morphology and lexicon indicate that in Mambay, the labial flap can be considered nothing other than an integral, contrastive phonological unit.