This book brings together 11 stories of citizens mobilizing for migrants, written by academic researchers, student-activists, and humanitarian professionals. The chapters draw on original field research on multifaceted citizen-led forms of aid that developed within and around European borders, from Serbia to Belgium and from Norway to Istanbul. They document how the world of international non-governmental organizations (NGOs) and their established practices of state collaboration, fundraising, accounting, outsourcing and being (un)accountable to beneficiaries and donors are increasingly complemented, questioned, confronted, bypassed and even replaced by grass-roots movements. These movements operate in a transnational yet localized and agile manner, across spaces in which border enforcement and state repression expose the political stakes of the global endeavour of sustaining lives at risk, otherwise known as humanitarianism. In this introduction, we conceptualize these spaces through an extended notion of humanitarian borders, rooted in critical geographical approaches, and offer a definition of citizen humanitarianism as a “craft”, a set of practices that can both disrupt and reinforce the spatialized inequalities that constitute liberal citizenship in Europe. We then outline the three sections of the book, focusing on humanitarianism, criminalization and politics respectively, and the individual chapters in them. The forms of grass-roots aid at the border that they detail, we argue, show that humanitarianism can no longer hide behind its purported neutrality and distance to avoid the political questions that have in fact always been at its core.