A central bank, reserve bank, or monetary authority is a banking institution granted the exclusive privilege to lend a government its currency. Like a normal commercial bank, a central bank charges interest on the loans made to borrowers, primarily the government of whichever country the bank exists for, and to other commercial banks, typically as a 'lender of last resort'. However, a central bank is distinguished from a normal commercial bank because it has a monopoly on creating the currency of that nation, which is loaned to the government in the form of legal tender. It is a bank that can lend money to other banks in times of need. Its primary function is to provide the nation's money supply, but more active duties include controlling subsidized-loan interest rates, and acting as a lender of last resort to the banking sector during times of financial crisis (private banks often being integral to the national financial system). It may also have supervisory powers, to ensure that banks and other financial institutions do not behave recklessly or fraudulently.

Most of the rich countries today have an "independent" central bank, that is, one which operates under rules designed to prevent political interference. Examples include the European Central Bank (ECB) and the Federal Reserve System in the United States. Some central banks are publicly owned, and others are privately owned. The United States Federal Reserve "is an unusual mixture of public and private elements".