Structurally robust tetradentate gold(III)-emitters have potent material applications but are rare and unprecedented for those displaying thermally activated delayed fluorescence (TADF). In this work, a novel synthetic route leading to the preparation of highly emissive, charge-neutral tetradentate [C^C^N^C] gold(III) complexes with 5-5-6 membered chelate rings has been developed through microwave-assisted C-H bond activation. These complexes show high thermal stability and with emission origin ( 3 IL, 3 ILCT and TADF) tuned by varying the substituents of the C^C^N^C ligand. With phenoxazine/diphenylamine substituent, we prepared the first tetradentate gold(III)-TADF emitters with emission quantum yields of up to 94 % and emission lifetimes of down to 0.62 µs in deoxygenated toluene. These tetradentate Au III -TADF emitters showed good performance in vacuum-deposited OLEDs with maximum EQEs of up to 25 % and LT 95 of up to 5280 h at 100 cd m -2 .