More than one hundred countries around the world have established national public health institutes (NPHIs) to coordinate and lead their public health systems. Some NPHIs, such as the US Centers for Disease Control and Prevention (CDC), South African National Institute for Communicable Diseases (NICD), Brazilian Oswaldo Cruz Foundation (FIOCRUZ), and Chinese Center for Disease Control and Prevention, have developed over time. Others, such as the Public Health Agency of Canada (PHAC), emanated in response to more recent global public health threats like severe acute respiratory syndrome (SARS). NPHI functionalities range from combatting primarily infectious diseases to comprehensive mandates to lead national efforts for prevention and control of both infectious and noncommunicable disease threats. The International Association of National Public Health Institutes (IANPHI), envisioned in 2001 and chartered in 2006, serves to link and catalyze the capacity of NPHIs around the world through a robust international professional and scientific network. IANPHI works closely with the World Health Organization (WHO) through a formal partnership agreement. The Bill & Melinda Gates Foundation, the Rockefeller Foundation, member dues and peer assistance, bilateral cooperative agreements, and private-sector partnerships support its activities. IANPHI’s members encompass more than five billion people across six continents. IANPHI is the only organization whose mission is to strengthen national public health institutes. To do this, IANPHI’s work focuses on (a) supporting a robust scientific community of NPHI directors through an annual meeting, a listserv, and collaborative activities; (b) developing and distributing guidelines and tools that strengthen NPHIs’ abilities to conduct and evaluate public health programs and efforts, including the IANPHI NPHI development framework, the Staged Development Tool, NPHI-to-NPHI evaluation guidance, and a best practices series; and (c) investing in projects designed to create NPHIs and strengthen public health systems in low-resource countries. IANPHI helps NPHIs by advocating for strong and well-supported NPHIs and providing timely information and insights for public health programs and actions.