The TOURSUS-EU proposal is designed to contribute to the definition of and the transition to a more sustainable model of tourism, which is one of the major issues of the EU. As a highly interdisciplinary project, TOURSUS-EU intends to introduce a new approach to measuring the impact of mass tourism on the economy and society, by analyzing data from important tourist destinations listed in the UNESCO World Heritage sites (Venice, Lisbon and Split). The proposal relies on the use of state-of-the-art knowledge and state-of-the-art analytical methods (Dynamic Panel Models, time series analysis, MultiCriteria Decision Analysis, and Big Data Analysis) to develop an innovative structured approach for the assessment and improvement of tourism sustainability. In particular, the project will allow for the quantitative evaluation of the effects of various factors on the negative developments in the tourism sector, as well as the assessment of the sustainable growth in tourism that will consider the negative effects that mass tourism generates. The expected results will be beneficial for both the scientific and the local community and will have an impact on the formation of management practices within tourist destinations, potentially to be adopted in other regions and tourist destinations in Europe and worldwide.