An I₂-mediated synthesis of phenanthridines via intramolecular sp³ C–H amination of readily accessible aniline precursors is reported. The present synthetic process is straightforward and applicable to a broad variety of unprotected aniline substrates, and provides facile and efficient access to phenanthridine derivatives. This C–H amination protocol does not use transition metals, is operationally simple, and can be achieved on a gram scale.