A fireteam is a small military unit of infantry. It is the smallest unit in the militaries that use it and is the primary unit upon which infantry organization is based in the British Army, Royal Air Force Regiment, Royal Marines, United States Army, United States Marine Corps, United States Air Force Security Forces, Canadian Forces, and Australian Army. Fireteams generally consist of four or fewer soldiers and are usually grouped by two or three teams into a squad or section.

The concept of the fireteam is based on the need for tactical flexibility in infantry operations. A fireteam is capable of autonomous operations as part of a larger unit. Successful fireteam employment relies on quality small unit training for soldiers, experience of fireteam members operating together, sufficient communications infrastructure, and a quality non-commissioned officer corps to provide tactical leadership for the team.

These requirements have led to successful use of the fireteam concept by more professional militaries. It is less useful for armies employing massed infantry formations, or with significant conscription. Conscription makes fireteam development difficult, as team members are more effective as they build experience over time working together and building personal bonds.