The present volume represents a unique contribution to its field. First of all, because it is the result of a common research effort by members of different European institutions of higher education, working together under the umbrella of the European Campus of City Universities Project (EC2U). The project brings together, with the goal of creating an integrated academic community, the Universities of Coimbra in Portugal, Iași in Romania, Jena in Germany, Pavia in Italy, Poitiers in France, Salamanca in Spain, and Turku in Finland. Secondly, the volume represents a special contribution because its authors, scholars of renown from different academic institutions across the European continent, contribute to the construction of a multidisciplinary and integrated concept of sustainability from the perspective of the social sciences. In this way, disciplines such as law, political science, economics, geography and sociology are combined, in order to develop the projection and meaning that the concept of sustainability can embody across the whole range of social science studies. Among the United Nations Sustainable Development Goals, number eleven corresponds to Sustainable Cities and Communities, and it specifically refers to the need to make cities and human settlements inclusive, safe, resilient and sustainable. Throughout this book, some of the key factors for achieving these objectives are discussed from the point of view of the human and social sciences, under a European theoretical framework.