The health system is a major contributor to Canada's greenhouse gas emissions, largely arising from the ways that care is organized and delivered. Nurses, representing the largest group of regulated healthcare professionals, are experts in the organization and delivery of care, and are uniquely and critically positioned to witness and address the harmful effects of climate crisis. Thus, sustainable health systems cannot be achieved without nurses. Yet, nurses' capacity to lead on issues of climate crisis and sustainability remains underdeveloped. We argue that the nursing profession needs to widely embrace climate crisis as a priority nursing problem and to take visible leadership on this issue. To enable the transformation of the health system toward sustainable and equitable delivery of care, health systems should incorporate a sustainability lens into strategic decision making, and implement and scale up nurse-led models of care. It is time to move beyond "engaging" or even "empowering" nurses to participate in sustainability initiatives. It is time for nurses to lead.