FIAT is a government-issued currency that is not backed by a commodity such as gold. It is an inconvertible paper money made legal tender by a government decree. Fiat money gives central banks greater control over the economy because they can control how much money is printed. Most modern paper currencies, such as the U.S. dollar, are fiat currencies.

The term FIAT derives from the Latin word fiat, meaning "let it be done" used in the sense of an order, decree or resolution.