Public health systems in India have weakened since the 1950s, after central decisions to amalgamate the medical and public health services, and to focus public health work largely on single-issue programs - instead of on strengthening public health systems' broad capacity to reduce exposure to disease. Over time, most state health departments de-prioritized their public health systems. This paper describes how the public health system works in Tamil Nadu, a rare example of a state that chose not to amalgamate its medical and public health services. It describes the key ingredients of the system, which are a separate Directorate of Public Health - staffed by a cadre of professional public health managers with deep firsthand experience of working in both rural and urban areas, and complemented with non-medical specialists-with its own budget, and with legislative underpinning. The authors illustrate how this helps Tamil Nadu to conduct long-term planning to avert outbreaks, manage endemic diseases, prevent disease resurgence, manage disasters and emergencies, and support local bodies to protect public health in rural and urban areas. They also discuss the system's shortfalls. Tamil Nadu's public health system is replicable, offering lessons on better management of existing resources. It is also affordable: compared with the national averages, Tamil Nadu spends less per capita on health while achieving far better health outcomes. There is much that other states in India, and other developing countries, can learn from this to revitalize their public health systems and better protect their people's health.