In the present work, we demonstrate a regioselective [2 + 2 + 2] cyclotrimerization of 1,3-diynes catalyzed by Ni⁰ to provide hexasubstituted benzenes (HSBs). HSBs have significant applications as functional materials and pharmaceuticals. The present protocol exhibited remarkable versatility, transforming 1,3-diynes with diverse alkyl, aryl, and heterocyclic groups to the corresponding HSBs. With the help of control experiments and density functional theory (DFT), the mechanism of the reaction and the origin of regioselectivity were elucidated.