Abstract: An inlet guide vane assembly for a centrifugal compressor includes a guide vane housing having an inlet side for receiving a fluid passing through the compressor at a first flow angle, an outlet side remote from the inlet side and a central axis extending between the inlet and outlet sides of the housing. The assembly has a first set of inlet guide vanes pivotally mounted within the guide vane housing, between the inlet side and the outlet side thereof, for impinging upon the fluid passing through the housing. The assembly includes a second set of inlet guide vanes pivotally mounted within the guide vane housing, between the first set of inlet guide vanes and the outlet side of the housing, for impinging upon the fluid passing through the housing after the fluid has passed through the first set of inlet guide vanes.