This paper studies the macroeconomic consequences of oil price shocks caused by innovations in the monopoly power in the oil market. Monopoly power is interpreted as oil producers’ ability to charge a markup over marginal costs. The authors propose a novel way to identify markup shocks based on meetings of OPEC and show that markup shocks have unique macroeconomic consequences compared to supply and demand shocks. In particular, global real economic activity expands when oil producers’ monopoly power rises. A general equilibrium model suggests that higher monopoly profits attract investments in oil producing capital, which drive down marginal costs and stimulate economic growth.