The 2021 Indianapolis 8 Hours was an endurance race held on 17 October 2021 at the Indianapolis Motor Speedway in Speedway, in Indiana, United States. The event was open to cars in GT classes, namely GT3 and GT4. It was the second running of the . It was also the second leg of the 2021 Intercontinental GT Challenge and the seventh and final race of the 2021 GT World Challenge America. The GT World Challenge America results were determined by the race results after three hours instead of the full eight hours.