The field of humanitarianism is characterised by profound uncertainty, by a constant need to respond to the unpredictable, and by concepts and practices that often defy simple or straightforward explanation. Humanitarians often find themselves not just engaged in the pursuit of effective action, but also in a quest for meaning. That is the starting point for this book. Humanitarian action has in recent years confronted geopolitical challenges that have upended much of its conventional modus operandi and presented threats to its foundational assumptions and legal frameworks. The critical interrogation of the purpose, practice and future of humanitarian action has yielded a rich new field of enquiry, humanitarian studies, and many thoughtful books, articles and reports. So, the question arose as to the most useful way to provide a critical overview that might serve to bring some definitional clarity as well as analytical rigor to the waves of critique and shifting sands of humanitarian action. Humanitarianism: A Dictionary of Concepts provides an authoritative analysis that attempts to rethink, rather than merely problematize or define the issues at stake in contemporary humanitarian debates. It is an important moment to do so. Just about every tenet of humanitarianism is currently open to question as never before.