Implementing Hospital Information System is an ultimately important practice that should be performed by hospitals in order to deliver accurate, timely, complete, and easily accessible data/information in an integrated manner. Given the specific characteristics of Indonesia, the objective of this research is to design an Information System Architecture as part of the Enterprise Architecture based on The Open Group Architecture Framework in order to support the Hospital Information System implementation in Indonesia. This research focuses on the hospitals basic processes, viz. the emergency processes, the inpatient processes and the outpatient processes. The integration aspect of the architecture should connect the hospitals with other related stakeholders. This research is a qualitative study by conducting interviews and observations in three government public hospitals, several directorate generals of the Indonesian Ministry of Health and a representative from the WHO. The result of this research is an integrated Information System Architecture model.