In many militaries, an executive officer (XO) is the second-in-command, reporting to the commanding officer (CO). The XO is typically responsible for the management of day-to-day activities, freeing the commander to concentrate on planning the unit's next move. The XO also takes charge in the absence of the commander, and the position is frequently a stepping stone to a command position.

In business, the executive officers are the top officers of a corporation, the chief executive officer (CEO) being the best-known type. The definition varies; for instance, the California Corporate Disclosure Act defines "executive officers" as the five most highly-compensated officers not also sitting on the board of directors.