This handbook is a foundational text which offers a comprehensive, accessible analysis of personal data protection law, and its significance to humanitarian organizations. Bringing together years of research on personal data protection principles, it outlines how humanitarian organizations can use these principles to uphold the rights and dignity of the most vulnerable. Reflecting the rapid evolution of new technologies, the handbook provides an in-depth analysis of the impacts of using specific technologies in humanitarian contexts. It raises awareness of the importance of data protection and suggests practical steps that humanitarian organizations can implement to process the personal data that they hold in a responsible manner that complies with personal data protection principles and requirements. With tailored advice and extensive, up-to-date research, this is a vital resource for humanitarian practitioners and lawyers, data protection authorities and researchers working on humanitarian affairs and personal data protection.