Currency intervention, also known as foreign exchange market intervention or currency manipulation, is a monetary policy operation. It occurs when a government or central bank buys or sells foreign currency in exchange for its own domestic currency, generally with the intention of influencing the exchange rate and trade policy.

Policymakers may intervene in foreign exchange markets in order to advance a variety of economic objectives: controlling inflation, maintaining competitiveness, or maintaining financial stability. The precise objectives are likely to depend on the stage of a country's development, the degree of financial market development and international integration, and the country's overall vulnerability to shocks, among other factors.

The most complete type of currency intervention is the imposition of a fixed exchange rate with respect to some other currency or to a weighted average of some other currencies.

There are many reasons a country's monetary and/or fiscal authority may want to intervene in the foreign exchange market. Central banks generally agree that the primary objective of foreign exchange market intervention is to manage the volatility and/or influence the level of the exchange rate. Governments prefer to stabilize the exchange rate because excessive short-term volatility erodes market confidence and affects both the financial market and the real goods market.

When there is inordinate instability, exchange rate uncertainty generates extra costs and reduces profits for firms. As a result, investors are unwilling to make investment in foreign financial assets. Firms are reluctant to engage in international trade. Moreover, the exchange rate fluctuation would spill over into the other financial markets. If the exchange rate volatility increases the risk of holding domestic assets, then prices of these assets would also become more volatile. The increased volatility of financial markets would threaten the stability of the financial system and make monetary policy goals more difficult to attain. Therefore, authorities conduct currency intervention.

In addition, when economic conditions change or when the market misinterprets economic signals, authorities use foreign exchange intervention to correct exchange rates, in order to avoid overshooting of either direction. Anna Schwartz contended that the central bank can cause the sudden collapse of speculative excess, and that it can limit growth by constricting the money supply.

Today, forex market intervention is largely used by the central banks of developing countries, and less so by developed countries. There are a few reasons most developed countries no longer actively intervene:

Developing countries, on the other hand, do sometimes intervene, presumably because they believe the instrument to be an effective tool in the circumstances and for the situations they face. Objectives include: to control inflation, to achieve external balance or enhance competitiveness to boost growth, or to prevent currency crises, such as large depreciation/appreciation swings.