This article introduces the special issue on the evolution of European Union development policy, against the background of fundamental challenges that have emerged since the 2009 Lisbon Treaty. The special issue's objective is to highlight the complex dynamics of a policy area that is called on to address the massive challenges of poverty, inequality, healthcare capacity, climate change, insecurity and weak governance in countries of the global south, and at the same time support European foreign policy objectives including political stability, migration management, access to resources and markets. In this introductory article, we attempt to sketch the broad outlines of the conceptual and practical dilemmas faced by a policy area that is supposed to be able to fix almost any problem. We observe that European development policy's evolution is driven by the tension between its raison d'être as a concrete expression of global solidarity and international cooperation, and its increasing instrumentalisation in the service of European economic and security interests. We highlight some of the key challenges that have emerged in the last decade, including rising populist nationalism and Brexit within Europe, the changing nature of relationships between Europe and countries who receive EU aid, and the changing nature of development cooperation itself, exemplified by the 2030 Agenda and the Sustainable Development Goals. We outline the specific contributions the articles in this special issue make to research and policy debates on the themes we raise in this introduction. We conclude that the battle between the forces of solidarity and instrumentality has evolved EU development policy into an impossibly complex arena of competing norms, practices and institutions, which raises many open questions for future research.