The EU-funded GO GREEN NEXT (GGN) project aims to deliver evidence-based policies and pilot projects in four European biogeographic regions, addressing the nexus between biodiversity, climate, and planetary health. Specifically, it will use nature-based solutions (NBS) and collaboration with global initiatives to reverse environmental degradation, particularly in urban areas vulnerable to climate change. A total of 19 partners and associated partners from North America, Switzerland, Norway, Spain, Austria, Netherlands, Finland, Germany, Malta, and three partners from Ireland will develop novel approaches to investigate how cities best can realise their climate neutral ambitions. GGN will deliver a comprehensive evidence-based policy-oriented approach model to convey how ecosystem health, physical activity, and human health are connected. NBS, or actions to protect, sustainably manage, and restore natural and modified ecosystems that address societal challenges effectively and adaptively, simultaneously benefiting people and nature, are among the strategies that have emerged to reverse the degradation of nature, notably in urban areas where changes are amplified. In cities, vulnerability to climate change and environmental degradation is high due to dense populations, critical infrastructure, and at-risk communities (e.g. vast differences across social-economic gradient). Cities offer an opportunity to accelerate the implementation of current solutions aligned with emerging strategies and policy initiatives (e.g. New European Bauhaus, 100 Climate Neutral and Smart Cities) combining to form what is termed a just green transition. This refers to a process of far-reaching sociotechnical change leading to a green and climate-neutral economy that preserves biodiversity and ensures social justice. GGN will address the biodiversity-climate-planetary health nexus, delivering positive policy and city/region pilot outcomes in four biogeographic regions across Europe (Cork City [Ireland], Klagenfurt [Austria], Paijat Hame Region [Finland], Malta) and with input from best practice globally.