With cracks in the liberalisation approach to capital flows appearing during the Asian Financial Crisis and subsequent crises in the early 2000s, policymakers and commentators began to understand that unregulated finance and cross-border flows could generate extreme financial instability. Capital controls have become widespread. For some, the controls are limited in nature and duration, but for others the controls are widespread and remain in place for an extended period. This shift has occurred at the same time the IMF has been more accepting of CFMs and in particular shifted its position on the extent to which they can be a source of instability in emerging markets. This chapter focuses on the role and legitimacy of CFMs. The chapter first provides a definition of CFMs and explains their role and impact in terms of capital flow management. Next, the chapter explains why CFMs are so controversial and elaborates on their operational aspects and overall desirability. The chapter concludes with a discussion on why CFMs remain difficult to manage from a macro level in the absence of a global regulatory framework.