The 2021 International GT Open was the sixteenth season of the International GT Open, the grand tourer-style sports car racing series founded in 2006 by the Spanish GT Sport Organización. It began on 15 May at Circuit Paul Ricard and endedat the Circuit de Barcelona-Catalunya on 24 October after seven rounds of two races each. This season the GT Cup Open Europe was brought into the International GT Open, meaning the GTC and GT4 cars shared grids with the headlining series.