Abstract: An important component of corporate governance is the regulation of significant transactions – mergers, acquisitions, and restructuring. This paper (a chapter in Oxford Handbook on Corporate Law and Governance, forthcoming) reviews how M&A and restructuring are regulated by corporate and securities law, listing standards, antitrust and foreign investment law, and industry-specific regulation. Drawing on real-world examples from the world’s two largest M&A markets (the US and the UK) and a representative developing nation (India), major types of M&A transactions are reviewed, and six goals of M&A regulation are summarized – to (1) clarify authority, (2) reduce costs, (3) constrain conflicts of interest, (4) protect dispersed owners, (5) deter looting, asset-stripping and excessive leverage, and (6) cope with side effects. Modes of regulation either (a) facilitate M&A – collective action and call-right statutes – or (b) constrain M&A – disclosure laws, approval requirements, augmented duties, fairness requirements, regulation of terms, process and deal-related debt, and bans or structural limits. The paper synthesizes empirical research on types of transactions chosen, effects of law on M&A, and effects of M&A. Throughout, similarities and differences across transaction types and countries are noted. The paper concludes with observations about what these variations imply and how law affects economic activity.