Marriages that involve the migration of at least one of the spouses challenge two intersecting facets of the politics of belonging: the making of the 'good and legitimate citizens' and the 'acceptable family'. In Europe, cross-border marriages have been the target of increasing state controls, an issue of public concern and the object of scholarly research. The study of cross-border marriages and the ways these marriages are framed is inevitably affected by states' concerns and priorities. There is a need for a reflexive assessment of how the categories employed by state institutions and agents have impacted the study of cross-border marriages. This collection of essays analyses what is at stake in the regulation of cross-border marriages and how European states use particular categories (e.g., 'sham', 'forced' and 'mixed' marriages) to differentiate between acceptable and non-acceptable marriages. When researchers use these categories unreflexively, they risk reproducing nation-centred epistemologies and reinforcing state-informed hierarchies and forms of exclusion. The chapters in this book offer new insights into a timely topic and suggest ways to avoid these pitfalls: differentiating between categories of analysis and categories of practice, adopting methodologies that do not mirror nation-states' logic and engaging with general social theory outside migration studies. This book will be of interest to researchers and academics of Sociology, Politics, International Relations, Social and Cultural Anthropology, Human Geography, Social Work, and Public Policy. Barring one, all the chapters in this book were originally published as a special issue in the Journal of Ethnic and Migration Studies.