BACKGROUND: Considered a global health crisis and human rights violation, addressing GBV remains a fundamental challenge in emergencies. GBV coordination is an essential element of every emergency response, ensuring that survivors have access to safe services and prevention and mitigation actions reduce GBV. As global commitment to addressing GBV intensifies, this thesis explored what influences effective GBV coordination during emergencies, to identify opportunities for strengthening systems in protracted and complex crises, using Lebanon as a case study. METHODS: I conducted a qualitative study using a scoping review, remote in-depth interviews (38), document review, and meeting observations (7). Data collection with stakeholders involved in Lebanon's response (2012-2022), spanned a two-year period (Oct 2019 - May 2022) and was analysed using framework analysis. FINDINGS: Findings are presented in three manuscripts which build on each other. A scoping review of GBV coordination in emergencies, summarises the global literature and presents an evidence informed framework for effective GBV coordination. Despite enhanced global commitments in recent years, findings indicate that GBV remains under-resourced with minimal progress on localization. GBV risk mitigation was compromised by weak accountability systems, and GBV prevention frequently deprioritised in emergencies. The second manuscript illustrates how the protracted emergency in Lebanon was a transformative force for GBV, promoting the establishment and expansion of GBV coordination and services nationwide. However, over-reliance on international leadership and funding, alongside limited government commitments to institutionalising systems, compromised sustainability. Findings emphasise the importance of dedicated, experienced coordinators who promote trust and collaboration with notable successes in advancing localization through mutually beneficial partnerships. GBV information management systems strengthened coordination, supporting funding mobilization and service delivery. The third manuscript examines Lebanon's compounded crises from 2019-2022 and underscores the need to adapt coordination efforts to evolving contexts and to promote a government-led response. Findings reveal that GBV coordination adapted well to the changing context, but service delivery by local actors was challenged by the multiple crises, and the expanding vulnerable populations required increased, multiyear funding. CONCLUSION: As the first of its kind, this study contributes to the evidence-base on GBV coordination, distilling several transferrable lessons. Findings demonstrate that effective coordination ensures GBV is adequately addressed in emergencies, improving emergency responses for women and girls. Recommendations to strengthen GBV coordination include funding and deploying dedicated GBV coordinators across all types of emergencies, and investing in GBV risk mitigation, data management systems, localization and prevention, through multiyear funding. Furthermore, the study highlights the need for dedicated attention to GBV coordination in public health emergencies.