In an air compressor, particularly for an internal combustion engine, which has a compressor housing with a flow duct structure and a recirculation arrangement including a bypass structure for recirculation some of the air entering the compressor wheel, a recirculating ring is arranged in the bypass flow structure around the compressor wheel and the ring has a plurality of flow passages distributed uniformly around its circumference with inflow orifices at the radial inner end in communication with the compressor flow duct and outflow orifice at the radial outer end in communication with a by-pass flow space.