Monetary policy is the process by which the government, central bank, or monetary authority manages the supply of money, or trading in foreign exchange markets. Monetary theory provides insight into how to craft optimal monetary policy.

Monetary policy is generally referred to as either being an expansionary policy, or a contractionary policy, where an expansionary policy increases the total supply of money in the economy, and a contractionary policy decreases the total money supply. Expansionary policy is traditionally used to combat unemployment in a recession by lowering interest rates, while contractionary policy has the goal of raising interest rates to combat inflation (or cool an otherwise overheated economy). Monetary policy should be contrasted with fiscal policy, which refers to government borrowing, spending and taxation.