Many-body light-matter systems are hybrid open quantum systems exhibiting both strongly correlated behaviors of matter and (in)coherent features of photons. They have emerged as a novel platform for studying nonequilibrium many-body quantum dynamics as well as for implementing new quantum technologies. The research focus of the “Many-Body Open Quantum Systems” (MB-OpenQS) Unit is to theoretically explore these systems via advanced analytical and numerical techniques, and uncover the underlying beautiful physics.