Abstract: An air deflector for the rear wheels of vehicles such as trucks and trailers is disclosed. The deflector consists of a fairing suspended beneath the truck or trailer body immediately in front of the rear wheels and extending completely across the width of the body. The surface of the fairing is curved in both a lateral and a vertical direction to deflect impinging air and entrained water or snow around or under the wheels. In a preferred form, the device is formed with a plurality of generally vertical grooves angled toward the center line of the vehicle. The grooves direct impinging air downwardly and between the rear wheels. The air deflector serves to suppress splashing and spraying of water from the roadway and of rain or snow, and reduces aerodynamic drag to improve handling and reduce fuel consumption.