This thought-provoking Research Handbook explores how penal policies are shaped, contested, and transformed. It examines the development of penal strategies, analysing why systems converge in some areas and diverge in others.Leading scholars and experts highlight emerging trends and challenges in the field, covering key topics including policy transfer, penal populism, technocratic approaches to penal policy, the influence of human rights, outcome assessment of penal policy decisions, and decarceration strategies. The chapters examine penal governance and the politics of crime and punishment, investigating how decisions about penal interventions are made, as well as the values, interests, and practical constraints which influence them. Combining theoretical examination and normative inquiry with a cross-national perspective and real-world analysis, the Handbook bridges theory and practice, serving as a foundational resource for engaging with contemporary debates in penal policy.This Research Handbook is an essential read for scholars and students of criminal law, criminal justice, and criminology. It is also beneficial for policymakers and criminal justice practitioners looking to better understand the complex forces shaping penal policy across diverse national and institutional contexts.