Massive stars are short lived and rare, yet they help to shape our Universe. They shine brightly in ultraviolet light, die in supernova explosions which enrich galaxies in elements such as oxygen, and sometimes their demise is associated with intense bursts of gamma-rays. IAU Symposium 250 charts our current understanding of the life, evolution and death of massive stars, both within the local Universe and when the Universe was in its infancy. These proceedings comprise over 50 extensive review and contributed papers spanning five contemporary themes: atmospheres of massive stars; the physics and evolution of massive stars; massive stars in the nearby Universe; hydrodynamics and feedback from massive stars in galaxy evolution; and massive stars as probes of the early Universe. Summaries of special sessions on magnetic massive stars and massive stars at low metallicity are also included.