Cladophorol A is a cGAS inhibitor that binds to the conserved adenosine nucleobase binding site of cGAS , thereby blocking its activity. At non-cytotoxic concentrations, Cladophorol A effectively inhibits the overactivation of the cGAS-STING pathway with an IC 50 of 370 nM. Cladophorol A holds potential for research on inflammatory diseases related to the overactivation of the cGAS-STING pathway.