Abstract: A shaftless compressor module has a module casing containing an axial chamber and an annular chamber which is coaxial with the axial chamber. An annular motor stator can be fixedly positioned in the annular chamber coaxially with the longitudinal axis of the axial chamber. An annular motor rotor can be positioned in the annular chamber coaxially with the annular motor stator. A shaftless impeller is rotatably mounted within the axial chamber. The impeller has a plurality of impeller passageways, with one end of each passageway being open to the inlet of the module casing and the other end of each passageway being located in a radially outer periphery of the impeller. Magnetic bearings can counter axial thrust and radial thrust. Annular gas seals can prevent gas flow through the second chamber. A plurality of these modules can be connected together to form a multiple stage shaftless compressor wherein each impeller can be driven at a different speed.