The paper presents three generations of theoretical models of currency crises. The models were drawing on the real crises. The first-generation models were developed after balance-of-payment crises in Mexico (1973-82), Argentina (1978-81), and Chile (1983). The second-generation models arose after speculative attacks in Europe and Mexico in 1990s. Finally, first attempts to built the third-generation models started after the Asian crisis in 1997-98. The paper also explains the mechanism of currency crisis, provides an overview of the crises literature, and defines the types of crises. This work is intended to summarize the current level of knowledge on the theoretical aspects of currency crises.