A hub-bearing unit is provided with a hub, rotatable, with an axially outer flange portion configured for engagement with a rotatable element of a motor vehicle, a bearing unit provided with a fixed radially outer ring, configured for engagement with a fixed element of the motor vehicle, a first, axially outer, crown of rolling bodies, and a second, axially inner, crown of rolling bodies, interposed between the radially outer ring and the hub. The radially outer ring is held in position with respect to the knuckle by a stop ring, positioned on the axially inner side of the radially outer ring in a seat formed on the radially outer ring.