Here is US President Donald Trump last week in his State of the Union Address: “A good life for American families also requires the most affordable, innovative, and high-quality healthcare system on Earth...Over 130 legislators in this chamber have endorsed legislation that would bankrupt our nation by providing free taxpayer-funded healthcare to millions of illegal aliens, forcing taxpayers to subsidise free care for anyone in the world who unlawfully crosses our borders...If forcing American taxpayers to provide unlimited free healthcare to illegal aliens sounds fair to you, then stand with the radical left. But if you believe that we should defend American patients and American seniors, then stand with me and pass legislation to prohibit free government healthcare for illegal aliens. This will be a tremendous boon to our already very strongly guarded southern border where, as we speak, a long, tall, and very powerful wall is being built.” Populism is the political order of the day. Trump is poised to win another presidential term. Boris Johnson may be the UK's Prime Minister for a decade. And don't forget Jair Bolsonaro, Narendra Modi, and Rodrigo Duterte.The idea that human beings are reshaping the contours of life and the possibilities for life is what we now call the Anthropocene. But when discussing the Anthropocene, we often make the mistake of assuming that human actions take place within fixed, static entities—countries, cities, communities. While we acknowledge the force of people, we pay too little attention to the flow. And yet it is the flow of people that is having far greater political impact and reach. Fear of migration is one of the main reasons for the emergence and expression of political populism. At last week's Global Health Lab, held at the London School of Hygiene & Tropical Medicine, we asked, “What is the impact of populism on global health?” Tim Haughton, Jonathan Kennedy, Chiara Rinaldi, and Martin McKee sought to answer that question with an audience of the School's students and faculty. The result was dispiriting. Populism is the idea of a pure and virtuous people uniting together against a corrupt establishment elite. It is a nativism where “people” means a particular ethnic or religious group. Migration is a powerful political force because it has given permission to political parties—especially parties of the radical right—to burnish their populist credentials, to demonise what they portray as undeserving foreigners, to create hostile environments, to erode the rights of minorities, to foster fears of invasion, and to use systems of social protection to implement systems of social exclusion and control. And yet we are paralysed. We genuinely don't know what to do. Do we ignore, confront, or copy the populists? We have no credible response.The political weaponisation of migration is a threat to ideas of universality, equity, and justice, ideas that are central to our concepts of health and health care. According to the International Organization for Migration (IOM), there are 272 million international migrants today—people living in a country other than their own. The IOM emphasises how small this number is: just 3·5% of the world's population. But that figure still represents over half the population of the European Union. It is a vast signal of human vulnerability. And please consider the trajectory. The highest number of internally displaced persons from violence and conflict on record today (41·3 million people). The increasing impact of a growing environmental crisis, with an estimated 1 billion climate refugees by 2100. The rising importance of food insecurity among migrants. The gradual feminisation of labour migration. And the threats to global health security from migration in an era of new infectious epidemics, as the 2019 novel coronavirus (2019-nCoV) outbreak shows only too tragically. Last week, The Lancet announced the launch of Lancet Migration, a new global collaboration to advance migration health. This initiative follows the 2018 publication of our UCL–Lancet Commission on Migration and Health, chaired by Ibrahim Abubakar. Miriam Orcutt is Lancet Migration's Executive Director and she will lead a programme of work on migration's intersection with universal health coverage, the climate emergency, and gender. The academic community can't retreat in the face of extreme political populism, which is fuelling racism, xenophobia, and hate. We have to do something. Lancet Migration is our effort to resist. Please join us.