A magnetic drive for coupling mechanical power to the interior of a high pressure vessel is disclosed. The drive includes an output or driven portion including a non-magnetic housing hermetically sealed to a wall of the vessel and containing an output shaft which extends into the vessel. The shaft is mounted for rotation in bearings contained within a cylindrical extension of the housing projecting into the vessel interior. The opposite end of the shaft carries a plurality of permanent magnet segments coaxial therewith and is located within a high pressure gas barrier of the housing external of the vessel. Input power is provided by an input shaft connected to a power source, the input shaft carrying a housing which is coaxial to the gas barrier and has permanent magnets therein which will interact with the output shaft magnets upon rotation of the input shaft to cause rotation of the output shaft. Integrally formed in the input housing is a centrifugal blower which will draw air along the gas barrier during rotation of the input shaft to provide cooling therefor. The structure is compact, is able to cool the entire gas barrier and keeps the formation of eddy currents and their inherent losses to a minimum.