Francois Langurs are part of the leaf-eating group of cercopithicines. They have a large stomach in which fibrous leaves can ferment and eventually be digested. They have a white stripe between the corners of the mouth and ear. Some of them have a pale or even golden-yellow color on the crown and neck. Otherwise they are uniformly black but the fur is fine and silky. A characteristic feature is the tuft of erect hairs on the crown. These monkeys have slender bodies, long tails and long slender hands.
They are excellent aerialists. These animals are diurnal and spend a good deal of time eating leaves, mostly young ones, and fruit of flowers when available. They can dig up roots including cultivated plants like potatoes.
They live in unstructured groups of 20 to 50 individuals with usually twice as many females as males. Many males live solitary lives or enter a group when mature. Babies are bright orange color when born. The color gradually changes to black as the baby grows older. The care of infants is shared by several females, not just the mother. Any lactating female may nurse any baby in the group.