This is the biggest of all river dolphins in the world. It can reach up to 2.80 m in body length and can weight up to 180 Kg. It has a corpulent body, not very hydrodynamic, but very flexible. The snout is long and has more or less 106 teeth which are heterodont, meaning that they have different types of teeth (incisive and molars), as opposed to marine dolphins that are homodont. The eyes are small but functional, adapted to the conditions of the turbid water they inhabit. The melon is pronounced, especially in adults. This structure serves as a good acoustic director for the sound waves they produce (echolocation). Contrary to marine dolphins, Inia can move their head from side to side because the cervical vertebrae are not fused together. The pectoral fins are broad and with great movement capacity. The caudal fin is low and elongated. The coloration pattern varies, generally when they are born they are grey and as they grow they can maintain this colour, become pink or be a mix of the two. The pink colour is determined genetically, but its intensity depends on the animal's physical activity.

This species is broadly distributed in the Amazon and Orinoco basins, in countries such as Colombia, Venezuela, Brazil, Bolivia, Ecuador and Peru. At the moment, two species are recognised: Inia boliviensis, in Bolivia, and Inia geoffrensis with two sub-species: I. geoffrensis geoffrensis in the Amazon and I. geoffrensis humboldtiana in the Orinoco.