A reduction gear includes a sun pinion and planet pinions driven by the sun pinion and rolling on a fixed ring gear. The device includes an oil tank, an oil supply duct and oil routing ducts. The device also includes an oil ejection device at the end of the fixed supply duct, the orientation of which includes a radial component directed away from a common axis of rotation, and a cylindrical device for recovering the oil that can move in rotation about the common axis of rotation. The oil ejection device is linked by at least one duct to a lubrication device for the gear formed by the cooperation of the teeth of at least one planet pinion with an adjacent pinion. This device feeds the ducts which supply the oil to the parts to be lubricated, by virtue of the action of the centrifugal field.