Optimizing humanitarian response through robust country-level inter-cluster / sector collaboration: The global increase in the number of active conflicts, internal population displacement, refugee crises, food and water scarcity, climate change, and rising communicable disease outbreaks, complicated by severely strained humanitarian resource capacity, are driving millions of people into devastating situations in many countries. The complex, interdependent nature of people’s needs cannot be addressed by individual sectors, which are themselves gravely underfunded. A more holistic approach is therefore needed to meaningfully save lives, livelihoods and sustain essential service provision. The below is a brief summary of the lessons learned over the past 3 years of collaboration, and the recommendations being proposed to stakeholders by the global Food Security, Health, Nutrition and WASH clusters.