A currency crisis is a type of financial crisis, and is often associated with a real economic crisis. A currency crisis raises the probability of a banking crisis or a default crisis. During a currency crisis the value of foreign denominated debt will rise drastically relative to the declining value of the home currency. Generally doubt exists as to whether a country's central bank has sufficient foreign exchange reserves to maintain the country's fixed exchange rate, if it has any. The crisis is often accompanied by a speculative attack in the foreign exchange market. A currency crisis results from chronic balance of payments deficits, and thus is also called a balance of payments crisis. Often such a crisis culminates in a devaluation of the currency. Financial institutions and the government will struggle to meet debt obligations and economic crisis may ensue. Causation also runs the other way. The probability of a currency crisis rises when a country is experiencing a banking or default crisis, while this probability is lower when an economy registers strong GDP growth and high levels of foreign exchange reserves. To offset the damage resulting from a banking or default crisis, a central bank will often increase currency issuance, which can decrease reserves to a point where a fixed exchange rate breaks. The linkage between currency, banking, and default crises increases the chance of twin crises or even triple crises, outcomes in which the economic cost of each individual crisis is enlarged.

Currency crises can be especially destructive to small open economies or bigger, but not sufficiently stable ones. Governments often take on the role of fending off such attacks by satisfying the excess demand for a given currency using the country's own currency reserves or its foreign reserves (usually in the United States dollar, Euro or Pound sterling). Currency crises have large, measurable costs on an economy, but the ability to predict the timing and magnitude of crises is limited by theoretical understanding of the complex interactions between macroeconomic fundamentals, investor expectations, and government policy. A currency crisis may also have political implications for those in power. Following a currency crisis a change in the head of government and a change in the finance minister and/or central bank governor are more likely to occur.

A currency crisis is normally considered as part of a financial crisis. Kaminsky et al. (1998), for instance, define currency crises as when a weighted average of monthly percentage depreciations in the exchange rate and monthly percentage declines in exchange reserves exceeds its mean by more than three standard deviations. Frankel and Rose (1996) define a currency crisis as a nominal depreciation of a currency of at least 25% but it is also defined at least 10% increase in the rate of depreciation. In general, a currency crisis can be defined as a situation when the participants in an exchange market come to recognize that a pegged exchange rate is about to fail, causing speculation against the peg that hastens the failure and forces a devaluation or appreciation.

Recessions attributed to currency crises include the Hyperinflation in the Weimar Republic, 1994 economic crisis in Mexico, 1997 Asian Financial Crisis, 1998 Russian financial crisis, the Argentine economic crisis (1999-2002), and the 2016 Venezuela and Turkey currency crises and their corresponding socioeconomic collapse.