A recent American Psychological Association Summit provided an urgent call to transform psychological science and practice away from a solely individual-level focus to become accountable for population-level impact on health and mental health. A population focus ensures the mental health of all children, adolescents, and adults and the elimination of inequities across groups. Science must guide three components of this transformation. First, effective individual-level interventions must be scaled up to the population level using principles from implementation science, investing in novel intervention delivery systems (e.g., online, mobile application, text, interactive voice response, and machine learning-based), harnessing the strength of diverse providers, and forging culturally informed adaptations. Second, policy-driven community-level interventions must be innovated and tested, such as public efforts to promote physical activity, public policies to support families in early life, and regulation of corporal punishment in schools. Third, transformation is needed to create a new system of universal primary care for mental health, based on models such as Family Connects, Triple P, PROmoting School-community-university Partnerships to Enhance Resilience, Communities That Care, and the Early Childhood Collaborative of the Pittsburgh Study. This new system must incorporate valid measurement, universal screening, and a community-based infrastructure for service delivery. Addressing tasks ahead, including scientific creativity and discovery, rigorous evaluation, and community accountability, will lead to a comprehensive strategic plan to shape the emergent field of public mental health. (PsycInfo Database Record (c) 2024 APA, all rights reserved).