<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The metal‐free, visible light‐induced benzannulation of biaryldiazonium salts with alkynes affords a variety of 9‐substituted or 9, 10‐disubstituted phenanthrenes via a cascade radical addition and cyclization sequence in the presence of eosin Y as a photoredox catalyst.</p> </abstract>