Due to the complex and constantly evolving nature of emergency management (EM), there is little consensus regarding many concepts used to describe informational structure of EM. This limits the efficiency and effectiveness of the decision making processes and can potentially lead to challenges in communication among disaster stakeholders and delays in the execution of emergency responses. This paper presented domain ontology for EM that can be useful to be shared across different emergency agencies and systems. The potential benefits of the proposed domain ontology include enabling better and faster decision making through explicit and shared structure of EM concepts and their relationships. We illustrate how domain ontology can facilitate more effective decision making processes in EM in the context of medical emergency coordination.