Binary stars are excellent probes of many aspects of modern astrophysics from nucleosynthesis to general relativity. In this session we will investigate all aspects of binary stars such as compact binaries (cataclysmic variables, double white dwarfs/neutron stars, X-ray binaries, gravitational wave sources etc.), chemically peculiar stars (e.g. barium and carbon-rich stars, sdO/B/RCrB stars), mass transfer and stellar mergers. We invite both observers and modellers, in particular PhD students, to participate in this exciting session!