There has been a very strong resurgence of interest in tax havens with the financial crisis of 2008, which brought to light the shadows of financial regulation and put public debts under pressure. It was not until several scandals occurred, however, that economists have really taken up this issue. This article briefly surveys the academic literature in economics about tax havens, trying to figure out what are these countries? How much do they weigh in the global economy? What do we know about cross-border flows? What is the extent of tax evasion by multinational firms? What is the impact on the revenue of other countries? What role do financial intermediaries play? How effective are the measures implemented to combat tax havens?