Aryl iodides are privileged intermediates in organic synthesis, underpinning cross-coupling chemistry, late-stage functionalization, and radiolabeling in medicinal chemistry. However, regioselective arene iodination remains a challenge, as traditional electrophilic iodination methods often require harsh conditions, exhibit poor selectivity, or suffer from limited functional group tolerance and substrate scope. We report a rapid and regioselective arene iodination enabled by Lewis acid activation of N-iodosaccharin. Iron(III) chloride and silver(I) triflimide were found to catalyze the efficient iodination of a broad range of electron-rich arenes at room temperature. The method displayed broad functional group tolerance and was applicable to complex substrates, including natural products and pharmaceuticals. Furthermore, the iodination was found to be compatible with cross-coupling reactions, allowing one-pot halogenation and arylation sequences for direct access to biaryl compounds.