Sustainability is a complex and abstract concept. However, policy-makers and representatives of global and regional associations need to assess and track the sustainable development of countries and regions to define a sustainability strategic path. The objective of this research is to propose and validate a methodology to define a simple but proper sustainability index that serves as a proxy for the identification of the segments of most and least advanced countries according to their achievement of the sustainable development goals defined by the United Nations (UN). Several well-known quantitative methodologies are used to first define a summarized index of sustainable development. Second, multicriteria decision-making methods are applied to determine the relative importance of the elements or dimensions comprising the sustainability concept. Then, the simulated judgments of a group of experts is used to compute a group weight vector by applying the Fuzzy Analytic Hierarchy Process (FAPH). Different aggregation methods are used to compute the importance that decision-makers assign to the several dimensions of sustainability. Finally, segments of countries generated with the clustering algorithm k-means are rated to identify sustainability benchmark segment(s) and groups of countries in need of support to attain the UN sustainability goals.