This article discusses the currency crisis, currency speculation (or foreign exchange speculation), and the relation between them. It begins by explaining what is a currency crisis, making use of the Asian crisis as a concrete example, which began in Thailand in 1997 and spread to several Asian countries. Next the concepts of speculation, currency speculation, and hedging, which is the opposite of speculation, are explained. Then a few issues related to currency crisis are discussed, and some of the recent theories of currency crisis are critically reviewed. Some of the main points developed in the article are as follows.