The IPMU conference is organized every two years with the aim of bringing together scientists working on information processing and the management of the many aspects of uncertainty. It also serves as an ideal forum for the exchange of ideas between theoreticians and practitioners in these and related areas. The 2026 edition of IPMU will take place at the Faculty of Economics of Sapienza University of Rome, Italy, in the nearby of the University city of Rome and the main train stations (Termini and Tiburtina). It celebrates the 40th anniversary from the first edition of the conference that took place in Paris, France. The choice of Rome for this special occasion is not a case since Rome and Paris are exclusively and reciprocally twinned, starting from April 1956. Sapienza University of Rome is one of the oldest universities of the world, being it funded in 1303 by Pope Boniface VIII, and is the largest university in Europe. Due to its strategic position, the Faculty of Economics allows to easily reach the plethora of monuments, historic hot-spots and wonderful sightseeing places that awarded to Rome the name of the Eternal city. Get ready for discussing cutting-hedge research on methods for the management of uncertainty and aggregation in one of the most beautiful cities of the world. On behalf of the Organizing Committee of the 21st IPMU Conference, we invite researchers to submit original research contributions (theoretical, methodological, applications) on a specific topic within the scope of the conference which includes (but is not limited to) the following topics: Theory, Methods and Tools: Measures of Information and Uncertainty Bayesian and Probabilistic Methods Evidence, Possibility and Utility Theories Imprecise Probabilities Fuzzy, Rough, Intuitionistic, etc, Sets and operators Fuzzy Logic and other non-classical Logics Multiple Criteria Decision Methods Aggregation Methods Knowledge Acquisition, Representation and Reasoning Graphical Models Machine Learning Evolutionary Computation Neural Networks Data Analysis and Data Science. Application Fields: Big Data Smart Cities Image Processing Intelligent Systems and Information Processing, Logistics, Transportation and Routing Information Retrieval and Fusion Agents E-Health, Medicine and Bioinformatics Finance Fuzzy Optimization