Flaring processes in the Sun, cool stars, and solar-like stars are observed across the electromagnetic spectrum revealing the stars’ atmospheric response to energy release processes. Solar observations with high spatial, spectral and/or temporal resolutions from many different instruments provide insights to plasma heating and cooling, change in ionization, and flows during flaring events. These processes are further investigated by means of detailed numerical simulations of magnetohydrodynamics and radiative transfer. Moreover, Sun-as-a-Star observations provide a link to flare phenomena observed in other stars. Stellar Activity is a growing subject, having attracted more attention in recent years given the observations of flares in G-, K- and M-type stars from the Kepler satellite and its implications to wider subjects, such as the search for exoplanets. We aim to bring together observers and theoreticians in Solar and Stellar activity to review and discuss recent advances in the fields, producing knowledge exchange between the two communities. In this session we welcome contributions discussing observational data analysis of stellar or solar flares, and theoretical or modelling efforts aimed to improve our understanding of the many physical processes in these energetic events, such as energy release and transport mechanisms, atmospheric response to energy input and, evolution of the magnetic field.