From its inception in the North American labour movement all the way to its inclusion in the Paris Agreement and current level of global proliferation, the concept of Just Transition has reached the pinnacle of global policy debates. Drawing on contributions to the Just Transition Research Collaborative (JTRC) project and a recently published volume1, we highlight the importance of historicising and rooting the Just Transition concept in the frontline communities and unions that are most directly affected and that initially imagined it. This, we believe, is key to ensuring that Just Transition is not simply a fashionable catchword but a concept that actually contributes to a socially just low-carbon transition. Just Transition: The Making and Globalisation of a Contested Concept The Origins of Just Transition: While the term ‘just transition’ was first used in 1995, it was part of an explicit strategy by unions and environmental justice activists in the USA and Canada that can be traced to the late 1980s. Drawing upon the US federal Superfund policy to clean up polluted sites, the Oil, Chemical and Atomic Workers Union suggested a Superfund for Workers in chemicals, weapons, and other toxic industries. The strategy of the union envisioned a robust green industrial policy, strong occupational, health and environmental rights and standards, alongside universal health care and the formation of an independent labour party. During the 1990s, US and Canadian unions promoted the strategy in collaboration with the environmental justice and elements of the environmental movement and in the context of systematic discussions between unions and environmentalists2. Just Transition fell off the US and Canadian union and environmentalist agenda after 2001. The Globalisation of Just Transition: The concept survived, however, because global union organisations, in collaboration with a number of national unions, including in the UK, Spain, Australia and South Africa, globalised the concept from the late 1990s onwards (Rosemberg 2020). The Spanish Comisiones Obreras and the associated Sustainlabour and ITUC, played a critical role in the diffusion of labour environmentalism globally, mainstreaming the Just Transition concept within international climate and environmental debates and processes3. During the Great Recession, when proposals for green jobs and green growth became more popular nationally and amongst intergovernmental organisations (IGOs), these unions sought to ensure that Just Transition remained on the agenda. Just Transitions Everywhere: More recently, the uptake of Just Transition has accelerated. Global climate activists started seeing its value and some transferred it back to their national movements. The ILO adopted its Just Transition guidelines in 2015. The ITUC established the Just Transition Centre (JTC) in 2016 and has pursued close collaboration between labour and sympathetic business (Moussu 2020). Other IGOs are also engaging the concept, as are various philanthropic and civil society organisations. Just Transition policies have been adopted by countries, such as Canada and Spain, by subnational units, such as Colorado and Scotland and by cities, such as Longmont, Colorado, and Jackson, Mississippi (Akuno 2020). C40, the global network of megacities has expressed its commitment to Just Transition. The growing number of references to Just Transition has increased the range of understandings of what it should mean, from more conventional and mainstream corporate social responsibility proposals to more transformative ideas that confront the current neoliberal economic system. A necessary step, therefore, is to identify and reflect on the various meanings and operationalisations of Just Transitions. Unions and Just Transitions Today Despite its union origins, Just Transition remains a contested concept within the world of labour. Some unions, particularly in extraction and construction, oppose Just Transition, due to both concerns over the implications of a transition and ideological reasons. Other unions have engaged the strategy but emphasised the social aspects over the urgency of a green transition. There are good reasons for that when states, business and environmentalists focus on urgency without justice. Overall, Just Transition is high on the agenda of the world of labour and there are many instances of unions debating and promoting Just Transition. These include the New Zealand Council of Trade Unions, various British and US unions and union related initiatives, the Alberta Federation of Labour in Canada, South African trade unions, Australian unions (Snell 2020) and others. But while some unions from the Global South...