Most of the emerging software-intensive systems nowadays are very large-scale ones, and inherently socio-technical. In this introduction to the special section on “Coordination in Large-Scale Socio-Technical Systems” we argue that the peculiar features of such emerging systems (up to millions of interacting components, lacking central control, mixing humans and artificial components) call for novel approaches to coordinate the overall activities and functionalities. Accordingly, we discuss some key-challenges to be faced by research in coordination models and technologies, and introduce the three articles of the special section.