With contributions from a team of renowned scholars, this two-volume Handbook is a comprehensive guide to the Distributed Morphology (DM) framework, providing an overview of all major theoretical issues in morphology. This volume, the first, covers the core components of DM, its historical context, and its foundational principles. It is divided into three parts; Part I introduces the basics of DM and compares it with alternative models, Part II delves into the core components of DM, and Part III addresses key issues for the syntax-morphology interface. Each chapter focuses on different theoretical issues, as well as empirical phenomena across a variety of languages. Filling a crucial gap in the domain of morphology, this volume is an essential resource for anyone who wants to understand the depth and scope of Distributed Morphology research.