SUN4Ukraine aims to bring together Ukrainian cities with the EU 100 Climate Neutral and Smart Cities Mission, through capacity building, technical expertise, twinning, multi-level governance and policy to support them in adopting climate neutrality targets and incorporating climate neutrality into reconstruction plans. SUN4Ukraine has selected and works with 12 Ukrainian Flagship Municipalities who receive technical support and participate in a capacity building programme to develop Climate Neutrality Plans, aiming for climate neutrality by 2050. A needs assessment is undertaken to understand the specific needs of each of the Flagship Municipalities informing detailed design of support. Technical support will guide Flagship Municipalities through the process of setting targets and the gap to be filled, identifying mitigation actions, engaging citizens and establishing new governance, designing Climate Neutrality Plans, and funding/ financing their implementation. Connections with funders and financiers will also be made to facilitate implementation. The capacity building programme will build the skills and capabilities of Flagship Municipalities, and include at its core, the peer learning, exchanges and study visits of Flagship Municipalities to Mission cities. A Ukrainian Cities Climate Hub will be established to bring Flagship Municipalities and other Ukrainian cities together to encourage mentoring, ongoing partnerships and replication. The lessons learned from technical support and the capacity building programme will be synthesised into guidance made available via the Hub and Mission Platform. Policy dialogues and recommendations, and good practices on multi-level governance will be developed to ensure Ukrainian cities can become climate neutral by 2050. A targeted communication and dissemination strategy will complement and support implementation. SUN4Ukraine will bring increased visibility to the Cities Mission and achieving its second objective of all European cities becoming climate neutral by 2050.