In a time of unprecedented internal and international migration, and their relative public health impacts, the UCL-Lancet Commission on Migration and Health provides a foundation for policy makers, advocates, health systems and communities to improve migration and health locally and globally. The Commission is the result of a two-year project led by 20 leading experts from 13 countries, and includes new data analysis, with two original research papers, and represents the most comprehensive review of the available evidence to date. The report, including its recommendations to improve the public health response to migration, will be launched on 8th December at the UN Intergovernmental Conference to adopt the Global Compact for safe, orderly and regular migration in Marrakech.