The first C-B bond-forming dearomative carboborylation of heteroaromatic compounds has been achieved using copper(I) catalysis. This reaction includes the regioselective addition of a borylcopper(I) intermediate to indoles, followed by the diastereoselective methylation of the resulting copper(I) enolate intermediate to afford the corresponding 3-boryl-2-methylindolines bearing a quaternary stereogenic center with excellent regio- and diastereoselectivity.