For more than 200 years, the taxonomy of Pithecia has been floating on the misunderstanding of a few species, in particular P. pithecia and P. monachus. In this revision, historical names and descriptions are addressed and original type material is examined. For every museum specimen, all location, collection, and museum data were recorded, and photographs and measurements of each skin, skull, mount, or fluid specimen were taken. The revision is based on work conducted in 36 museums in 28 cities from 17 countries in North America, South America, Europe, and Japan, resulting in the examination of 876 skins (including mounts and fluids), 690 skulls, and hundreds of photographs taken by the author and by colleagues in the field of living captive and wild sakis of all species, and through internet searches. Per this revision, there are 16 species of Pithecia: five currently recognized, three reinstated, three elevated from subspecies level, and five newly described.