In a moment defined by drastic cuts to health and social services, disappearing public health data, increasing costs of health care, and resurgent infectious diseases, funders must act with unprecedented urgency and scale to protect the most vulnerable and preserve hard-won health gains. Meeting this crisis demands deep, authentic engagement with communities, strong collaboration among funders, and bold partnerships that extend beyond philanthropy. Health funders have mobilized during past emergencies, including the COVID-19 pandemic, the Medicaid unwinding, and climate-driven disasters, but the breadth and stakes of today’s challenges eclipse anything in recent memory. Given the importance of partnerships to effective response, it is striking how little we know about funder collaboration and what strategies are most impactful.