Insurance is becoming the frontline test of global sustainability. Unlike other financial actors, insurers cannot defer or obscure rising risk: they must price it annually, making climate-driven pressures visible through withdrawal, soaring premiums, and the emergence of “insurance deserts.” As extreme weather events intensify, and losses become correlated rather than diversifiable, traditional insurance models are breaking down, threatening housing markets, infrastructure finance, and social stability. These stresses reveal a growing mismatch between where risks are created, and who ultimately bears them. Innovation within insurance, while valuable, cannot resolve systemic risk on its own. Instead, resilience must become an organising principle: reducing risk at source, investing ahead of loss, and building fair public–private risk-sharing frameworks. Whilst the future of insurance is increasingly co-dependent on sustainability, the implications of this have yet to be fully recognised. The chapter sets out five principles for moving the nexus forward. Insurance is where sustainability becomes economically unavoidable and where systemic reform is urgently required.