This chapter examines the evolution of the JGT concept from a historical perspective, connecting its major conceptual and operational milestones to the development of the international climate policy agenda, from its origins to its current interpretation in practice, policy, and research. The concept of a just green transition is a multidimensional construct that rests on the notions of social justice (just), environmental sustainability (green), and socio-technical change (transition). Initially, the concept was conceived as a set of measures supporting workers who lost their jobs due to processes of industrial reconversion (mitigation phase). Later, the concept was explored from an environmental justice perspective and promoted as a tool to prevent social impacts linked to climate policies (adaptation phase). More recently, the concept has been framed in the broader agenda of transition governance and mainstreamed as strategic policy pursuing a societal shift towards a more sustainable future (transformation phase). The evolution of the green just transition concept from an applied, unidimensional, single-actor, ad-hoc set of palliative measures to a rather strategic, multidimensional, multi-actor policy planning framework enabling transformative societal change has manyfold implications for territorial governance. This chapter explores such repercussions from the perspective of the EU and Western Balkan environmental and climate policy frameworks.