A highly efficient hydroxylation of (hetero)aryl halides using water as a hydroxyl source via Ni catalysis promoted by PhSiH 3 under thermal catalysis is reported. This methodology provides a general procedure to obtain diverse multifunctional pharmaceutically phenols and polyphenols, some of which are proven challenging to be synthesized using literature methods. Mechanism studies demonstrated that the addition of PhSiH 3 led to the generation of active Ni(I) species, which catalyze the hydroxylation via a Ni(I)-Ni(III) pathway.