The most dangerous threat to health and health equity today is anti-globalism—a denial of evidence pointing to the intrinsic interdependence of human beings; a refusal to accept the transnational nature of risks to our wellbeing; and an antipathy to institutions and individuals promoting cosmopolitan values. Anti-globalism lies behind the failure of governments to accelerate actions to address the climate crisis, is responsible for the failure of nations to coordinate their responses to the COVID-19 pandemic, and underlies the savage xenophobia directed towards those fleeing conflict and repression. But why is anti-globalism a subject for the decolonisation of medicine and global health? Because anti-globalism is nothing less than a project of recolonisation. Anti-globalism is the ideology of ultranationalist political movements that aim to embed inequalities between peoples, solidify asymmetries of power between nations, and expand the privileges of international elites. Anti-globalists seek to maintain the dominance of the rich over the poor and the powerful over the weak. The objective of anti-globalists is to perpetuate one country's control over another, to permit one people's exploitation by another. If anti-globalists succeed in their strategy of recolonisation, hopes for progress towards a more equitable distribution of health will flounder. The territory on which global health practitioners and activists must fight can be clearly mapped out. We can see the contours of ultranationalism in the regimes of Vladimir Putin, Donald Trump, Jair Bolsonaro, Recep Tayyip Erdoğan, Narendra Modi, Viktor Orbán, and Boris Johnson. The language used by these political leaders and the support they have inspired foster ethnic and religious division, fear of immigration, and panic about losing what is seen as the traditionally dominant culture of their nation. The pattern is a familiar one. Nationalist leaders celebrate a vision of their country's history and identity that evolves from glory to decline. They blame an insidious “globalism”. Those same leaders undermine the rule of law by attacking independent judiciaries. They target institutions, such as universities and the media, which are independent voices of dissent. They manipulate school curricula to indoctrinate new generations into these national myths. They lie frequently. They show contempt for compromise. They approve of natural hierarchies within society. They foster a sense of victimhood. They attack cosmopolitan elites and the internationalism they advocate. They encourage fear of immigration, giving oxygen to Renaud Camus's racist theory of The Great Replacement. They promote competition as the means to judge not only success but also worth. They preside over the gradual corruption of the state, from undermining bulwarks of integrity and accountability to breaking international law. They try to evade scrutiny. They feed off polarisation, a divided opposition, and growing insecurities and resentments. Some even endorse political violence. Unquestioning patriotism takes priority over universal values and individual rights. As Robert O Paxton concluded in The Anatomy of Fascism (2004), fascist movements exist in all democratic societies. Whether they take root or achieve power depends on our ability to detect their presence and to ensure they do not become an attractive “lure of untried possibility”. “There remains”, wrote Paxton, “the element of human choice”. It is a moment now for those working in medicine and global health to exercise that choice. Decolonisation is not merely about reconstructing the knowledge that underpins global health. It is not another domain of a culture war. And it cannot be reduced to the simplistic call for “revolution”. In Neo-colonialism: the Last Stage of Imperialism (1965), Kwame Nkrumah wrote about the need “to secure a world realignment so that those who are at the moment the helpless victims of a system will be able in the future to exert a counter pressure”. Anti-globalists fear nothing more than such a “world realignment”. They seek to cement existing hierarchies within societies and among nations to preserve their own power and influence. To decolonise global health means to challenge and to erase these hierarchies, to redistribute power and influence at all levels of global governance, from the P5 of the UN Security Council to the leadership of global health institutions. Decolonisation means a commitment to ending systemic racism. Decolonisation, above all, means turning a reimagining of the world into a forward looking political project.