The M9 half-track was a half-track produced by International Harvester in the United States during World War II for lend-lease supply to the Allies. It was designed to provide a similar vehicle to the M2 half-track car. It had the same body and chassis as the M5 half-track but had the same stowage and radio fit as the M2 half-track.

A half-track is a civilian or military vehicle with regular wheels at the front for steering and continuous tracks at the back to propel the vehicle and carry most of the load. The purpose of this combination is to produce a vehicle with the cross-country capabilities of a tank and the handling of a wheeled vehicle.