A duty officer or officer of the day is worker assigned a position on a regularly rotational basis. While on duty, duty officers attend to administrative tasks and incidents that require attention regardless of the time of day, in addition to the officer's normal duties.

A duty officer is a professional responsible for the immediate, day-to-day oversight of an organization’s operations during a specific shift or "duty" period. This role exists across many sectors—including emergency services, hospitality, corporate security, and the military—and the core mission is to serve as the primary point of contact for any issues that arise. The duty officer monitors ongoing activities, manages staff on the floor, and ensures that all safety and operational protocols are strictly followed. Crucially, they are the "first responder" for emergencies or unexpected incidents; if a crisis occurs, they must think quickly, coordinate with various departments, and make high-stakes decisions to maintain order and safety. They also handle administrative tasks such as preparing incident reports and conducting handovers for the next shift. In essence, the duty officer acts as the "eyes and ears" of management, providing a consistent leadership presence that ensures the facility or organization continues to function efficiently and safely around the clock, regardless of whether the senior executive team is physically present.