A separator for separating oil mist from the crankcase ventilation gas of an internal combustion engine, especially of a motor vehicle. The separator includes a gas purification chamber inside which a rotatably mounted centrifugal rotor is arranged. The gas purification chamber has a crude gas inlet, a pure gas outlet, and an oil outlet. The crankcase ventilation gas can be conducted into a radially internal zone of the centrifugal rotor via the crude gas inlet, while pure gas that is liberated from oil mist can be discharged from the gas purification chamber via the pure gas outlet, and oil separated from the gas can be discharged from the gas purification chamber via the oil outlet. The separator further includes a rotary drive for the centrifugal rotor. The rotary drive is disposed in a drive chamber of the separator, can be operated using pressurized lubrication oil of the internal combustion engine, and is connected to the centrifugal rotor by means of a shaft extending from the drive chamber into the gas purification chamber, from which the drive chamber is separated. The rotary drive is formed by at least one thrust nozzle which is connected to the shaft and to which the pressurized lubrication oil of the internal combustion engine can be fed. The separator includes at least one part of a base that forms the separation between the gas purification chamber and the drive chamber and extends into the drive chamber, the part of the base being fitted with a seat for a bearing of the shaft. The bearing is located at a distance from the centrifugal rotor.