This book presents and discusses the law of third sector organizations in a selected number of European Union countries and in a comparative perspective, with the aim of providing a common basis for further legal analyses or legislative advancements both at the national and supranational level. The book is divided into two parts. Chapters in Part I present the ways in which each national jurisdiction deals with the group of organizations identified by the authors as “third sector organizations”, regardless of the ways in which these organizations are denominated or are commonly known in each country or the place in which their regulation is found. Chapters in Part II share a synthesis and comparative approach and draw the lines for further developments of the research activity culminated in the book.