This chapter reviews the rich literature on regulatory enforcement, discusses the status quo in research and practice, and highlights the challenges of different approaches, illustrated with examples from the enforcement of EU law and regulation. It first reviews classic debates on regulatory enforcement, including deterrence-based enforcement, compliance-based enforcement and mixed strategies such as responsive regulation. From there, it reviews recent trends in regulatory enforcement, including (enforced) self-regulation, outsourced and privatized enforcement, regulatory intermediaries, risk-based regulation and the embracing of information technology and insights from the behavioural sciences in regulatory enforcement. The chapter concludes with suggestions for future research on this topic.