A turbocharger, comprising: a turbine wheel affixed to one end of a rotatable shaft and disposed in a turbine housing configured to direct exhaust gas from an engine into the turbine wheel for rotatably driving the turbine wheel and shaft; a compressor wheel affixed to an opposite end of the shaft, the compressor wheel comprising a first impeller and a second impeller each having a hub (24h, 26h) and a plurality of blades (24b, 26b) extending generally radially out from the hub, the blades of each impeller defining an inducer(24i, 26i) at a front side of the impeller through which air is ingested into the impeller, each impeller having a back side opposite from the front side, the back side of the first impeller facing toward the turbine wheel and the back side of the second impeller facing the back side of the first impeller; a compressor housing containing the compressor wheel, the compressor housing defining a circumferentially extending volute surrounding a radially outer periphery of the compressor wheel for receiving pressurized air discharged from each of the impellers, the compressor housing further defining a tubular first inlet duct arranged to direct air in a first axial direction into the inducer of the first impeller; and a second inlet duct formed separately from the compressor housing for directing air into the inducer of the second impeller, wherein each impeller has its own air inlet; and the air pressurised by each impeller is discharged into a common volute, characterised in that the second inlet duct comprises a tubular conduit having an upstream end and a downstream end and extends generally parallel to the first axial direction, the tubular conduit being bifurcated at the downstream end into a pair of separate duct branches (58a, 58b) that divide an air stream flowing through the tubular conduit into a pair of separate air streams, each duct branch configured to turn the respective air stream from the first axial direction to a radially inward direction generally opposite to that of the other duct branch, each duct branch having a radially inner end (60a, 60b) that joins with that of the other duct branch such that the air streams are re-joined, the radially inner ends being configured to turn the re-joined air stream to a second axial direction opposite to the first axial direction and direct the re-joined air stream into the inducer of the second impeller. a turbine wheel affixed to one end of a rotatable shaft and disposed in a turbine housing configured to direct exhaust gas from an engine into the turbine wheel for rotatably driving the turbine wheel and shaft; a compressor wheel affixed to an opposite end of the shaft, the compressor wheel comprising a first impeller and a second impeller each having a hub (24h, 26h) and a plurality of blades (24b, 26b) extending generally radially out from the hub, the blades of each impeller defining an inducer(24i, 26i) at a front side of the impeller through which air is ingested into the impeller, each impeller having a back side opposite from the front side, the back side of the first impeller facing toward the turbine wheel and the back side of the second impeller facing the back side of the first impeller; a compressor housing containing the compressor wheel, the compressor housing defining a circumferentially extending volute surrounding a radially outer periphery of the compressor wheel for receiving pressurized air discharged from each of the impellers, the compressor housing further defining a tubular first inlet duct arranged to direct air in a first axial direction into the inducer of the first impeller; and a second inlet duct formed separately from the compressor housing for directing air into the inducer of the second impeller, wherein each impeller has its own air inlet; and the air pressurised by each impeller is discharged into a common volute, characterised in that the second inlet duct comprises a tubular conduit having an upstream end and a downstream end and extends generally parallel to the first axial direction, the tubular conduit being bifurcated at the downstream end into a pair of separate duct branches (58a, 58b) that divide an air stream flowing through the tubular conduit into a pair of separate air streams, each duct branch configured to turn the respective air stream from the first axial direction to a radially inward direction generally opposite to that of the other duct branch, each duct branch having a radially inner end (60a, 60b) that joins with that of the other duct branch such that the air streams are re-joined, the radially inner ends being configured to turn the re-joined air stream to a second axial direction opposite to the first axial direction and direct the re-joined air stream into the inducer of the second impeller.