Competitiveness and sustainability are multidimensional concepts that are often measured using multiple indicators. In this paper, we are going to measure sustainable competiveness using a unique index. To do this, we work with the European Regional Competitiveness Index (RCI), which provides an overall but summarised view of territorial competitiveness for each of the NUTS 2 (Nomenclature of Units for Territorial Statistics) regions of the 28 European Union Member States. Although the RCI is a complete competitiveness index, it presents some limitations, as it does not take into account any aspect of an environmental character. In order to assess the sustainability of the NUTS 2 regions, several environmental indicators have been added to the RCI (emission of CO 2 , waste generated per capita, environmental investment of the public and private sector, among others). The Technique for Order Preference by Similarity to Ideal Solution permits aggregating these indicators to a new unified measurement of the regional sustainable competitiveness, the European Regional Sustainability Competitiveness Index, henceforth RSCI.