A military staff or general staff (also referred to as army staff, navy staff, or air staff within the individual services) is a group of officers, enlisted and civilian staff who serve the commander of a division or other large military unit in their command and control role through planning, analysis, and information gathering, as well as by relaying, coordinating, and supervising the execution of their plans and orders, especially in case of multiple simultaneous and rapidly changing complex operations. They are organised into functional groups such as administration, logistics, operations, intelligence, training, etc. They provide multi-directional flow of information between a commanding officer, subordinate military units and other stakeholders. A centralised general staff results in tighter top-down control but requires larger staff at headquarters (HQ) and reduces accuracy of orientation of field operations, whereas a decentralised general staff results in enhanced situational focus, personal initiative, speed of localised action, OODA loop, and improved accuracy of orientation.

A commander "commands" through their personal authority, decision-making and leadership, and uses general staff to exercise the "control" on their behalf in a large unit. The traditional role of the general staff in control role has evolved from the simpler "C2" (command and control) to "C3" (C2 with addition of "communication", such as PsyOps) to "C4" (C3 with addition of "computers", such as IT and networks) to C4I2 (C4 with addition of "intelligence" and "interoperability") to "C5I" (C4 with addition of "collaboration" and "intelligence") to "C6ISR" (subsumes C4I2 and C5I by combining C4 element of "command, control, communications and computers" with addition of 2C "cyber-defense and combat systems" (e.g. aegis) and ISR elements of "intelligence, surveillance, and reconnaissance").

Most NATO nations, including the United States and most European nations, use the Continental Staff System which has origin in Napoleon's military. The Commonwealth Staff System, used by most of the Commonwealth, has its origin in the British military.