Abstract Introducing the primary amino group into aromatic ring is one of the most important study issues in organic chemistry, particularly for the pharmaceuticals and agrochemicals chemistry. Herein, we describe a photoinduced direct C−H amination of arenes with ammonia via the site‐selective C−H thianthrenation that forms a new C−N bond with excellent regioselectivity. The reaction is carried out under mild conditions, and with a wide range of functional group tolerance, such as sensitive −Cl, −Br, and −OH groups which are poorly tolerated in conventional approaches. Moreover, the synthetic utility of our amination protocol has been confirmed through late‐stage modification and gram‐scale synthesis of complex drug‐like molecules.