A floating exchange rate or fluctuating exchange rate is a type of exchange rate regime wherein a currency's value is allowed to fluctuate according to the foreign exchange market. A currency that uses a floating exchange rate is known as a floating currency.

There are economists who think that, in most circumstances, floating exchange rates are preferable to fixed exchange rates. As floating exchange rates automatically adjust, they enable a country to dampen the impact of shocks and foreign business cycles, and to preempt the possibility of having a balance of payments crisis.

However, in certain situations, fixed exchange rates may be preferable for their greater stability and certainty. This may not necessarily be true, considering the results of countries that attempt to keep the prices of their currency "strong" or "high" relative to others, such as the UK or the Southeast Asia countries before the Asian currency crisis.

The debate of making a choice between fixed and floating exchange rate regimes is set forth by the Mundell–Fleming model, which argues that an economy (read: government) cannot simultaneously maintain a fixed exchange rate, free capital movement, and an independent monetary policy. It can choose any two for control, and leave the third to market forces.

In finance, an exchange rate (also known as the foreign-exchange rate, forex rate or FX rate) between two currencies is the rate at which one currency will be exchanged for another. It is also regarded as the value of one country’s currency in terms of another currency. For example, an interbank exchange rate of 91 Japanese yen (JPY, ¥) to the United States dollar (US$) means that ¥91 will be exchanged for each US$1 or that US$1 will be exchanged for each ¥91. Exchange rates are determined in the foreign exchange market, which is open to a wide range of different types of buyers and sellers where currency trading is continuous: 24 hours a day except weekends, i.e. trading from 20:15 GMT on Sunday until 22:00 GMT Friday. The spot exchange rate refers to the current exchange rate. The forward exchange rate refers to an exchange rate that is quoted and traded today but for delivery and payment on a specific future date.

In the retail currency exchange market, a different buying rate and selling rate will be quoted by money dealers. Most trades are to or from the local currency. The buying rate is the rate at which money dealers will buy foreign currency, and the selling rate is the rate at which they will sell the currency. The quoted rates will incorporate an allowance for a dealer's margin (or profit) in trading, or else the margin may be recovered in the form of a "commission" or in some other way. Different rates may also be quoted for cash (usually notes only), a documentary form (such as traveller's cheques) or electronically (such as a credit card purchase). The higher rate on documentary transactions is due to the additional time and cost of clearing the document, while the cash is available for resale immediately. Some dealers on the other hand prefer documentary transactions because of the security concerns with cash.