Resistive Plate Chambers, RPCs, are gaseous ionization detectors with planar resistive electrodes, devised by R. Cardarelli and R. Santonico about 40 years ago. Since then, they have been widely used in High Energy as well as in Nuclear and Astro-particle Physics, as muon-trigger and timing detectors. The Resistive Plate Chamber workshop is a biennial appointment dedicated to the state-of-the-art and to future developments of this detection technique. The XV edition has been held in Rome from February 10th to 14th, 2020 at the University of Tor Vergata, where one of the first editions had been hosted. The contributions to the workshop outlined the main interests of the community, from the status of present large systems to future applications, in terms of aging, gas-mixture studies, constructive techniques as well as Front-End and DAQ electronics. Simulations of elementary processes inside the gas, machine-learning-based approaches to data analysis and applications outside of particle and astro-particle physics have also been presented. The editorial board of the conference proceedings is composed by Barbara Liberti (INFN-Roma2), Alessandro Paoloni (INFN-LNF) and Paolo Camarri (INFN-Roma2 and University of Rome Tor Vergata).