We are part of the UCL Commission on Migration and Health. Migration is one of the most important public health issues facing the world today. International and internal migration is increasing, triggered by displacement of large numbers of people due to conflict, natural disasters, search for safety, and economic opportunities. A well considered and humane policy course offers extraordinary opportunities to make major gains in health and wellbeing. We are conducting the Million Migrant Study as part of our work in this area, which will create a population-based cohort study to describe the hospital-based healthcare and mortality outcomes of 1.5 million non-European Union (EU) migrants and refugees in England.