Foreign exchange markets are financial platforms where foreign exchange buying and selling transactions take place. In foreign exchange markets, the currencies of different countries around the world are exchanged. Foreign exchange markets are often referred to as Forex (Foreign Exchange, FX) and can be traded around the clock worldwide through online trading platforms. Therefore, foreign exchange markets are recognised as the largest and most liquid financial market. In Turkey, foreign exchange markets consist of financial platforms, banks, bureaux de change and financial institutions where international foreign exchange transactions take place. Many currencies such as the US Dollar (USD), Euro (EUR), Pound (GBP), Japanese Yen (JPY), which are considered convertible against the Turkish Lira (TRY), are traded. The value of the Turkish lira against foreign currencies is determined by the supply and demand conditions in the foreign exchange market and changes instantaneously. The functioning of foreign exchange markets is quite complex and can be affected by many factors. The stability of foreign exchange markets in Turkey is ensured by the Central Bank of the Republic of Turkey. In Turkey, foreign exchange markets were liberalised in 1980 with a free exchange rate system. Thus, the country's economy has become more competitive and international trade has increased. In this process, Turkey has faced many financial crises and economic difficulties and necessary arrangements have been made. Foreign exchange markets have an important share in financial markets both in Turkey and in the world. Therefore, the development of foreign exchange markets is very important for the stable growth of national economies. This study provides information on the structure and functioning of foreign exchange markets, the development of foreign exchange markets in Turkey, the effects of crises, exchange rate systems and foreign exchange transactions. The study is expected to be useful for researchers, policy makers and investors interested in foreign exchange markets.