The 2021 Indianapolis 8 Hours was an endurance race held on 17 October 2021[1] at the Indianapolis Motor Speedway in Speedway, in Indiana, United States.

The event was open to cars in GT classes, namely GT3 and GT4.

The race was run on the SCCA Runoffs layout, not the INDYCAR Grand Prix layout as was done the previous year, as it was made necessary as a result of kerbing damage in the Turn 5-6 chicane during the Verizon 200 NASCAR-INDYCAR meeting.

The Runoffs course utilised the old Formula One course with the newer Snake Pit section.

Pole positions in each class are denoted in bold.