IAU Symposium 361 brought together observational and theoretical astrophysicists to discuss all aspects of massive stars: their formation, evolution, demise as supernovae and GRBs, and gravitational waves from mergers of stellar-remnant neutron stars and black holes. The special focus was on massive stars in the early Universe, how they compare with massive stars in our Galaxy and with low-metallicity galaxies in the local Universe, anticipating new results from HST's ULLYSES and JWST. The volume includes contributions from the virtual preview meeting (May 2021) held online due to COVID-19 restrictions, and the in-person meeting (May 2022) held in Ballyconnell, Co. Cavan, Ireland. More than 200 participants from 32 countries contributed through highlight talks on exciting new results and wide-ranging contributed talks and posters covering the latest research from cool supergiants to hot Wolf-Rayet stars.
