This introduction serves to contextualize six PROTECT country case study reports from the EU Horizon 2020 PROTECT research project. Drawing on ethnographic studies in selected arrival ports in France, Italy, Spain, Greece, Canada and South Africa, the reports discuss how actors and stakeholders in the field level governance of migration and international protection understand and operationalise the notion of vulnerability. In this introduction, we first discuss how the notion of vulnerability is understood in the Global Compacts for Migration and on Refugees. We go on to present some analytical approaches to vulnerability to frame the reports, and end by drawing out some cross-cutting themes from the case studies. In particular, we highlight certain structural challenges and adverse effects related to the increasing centrality of vulnerability in migration governance.