Existing population health indicators tend to be out-of-date, not fully available at local levels of geography, and not developed in a coherent/consistent manner, which hinders their use in public health. The PopHR platform aims to deliver an electronic repository that contains multiple aggregated clinical, administrative, and environmental data sources to provide a coherent view of the health status of populations in the province of Quebec, Canada. This platform is designed to provide representative information in near-real time with high geographical resolution, thereby assisting public health professionals, analysts, clinicians and the public in decision-making. This paper presents our ongoing efforts to develop an integrated population health indicator ontology (PHIO) that captures the knowledge required for calculation and interpretation of health indicators within a PopHR semantic framework.