A fireteam is the smallest organization that ground forces are assigned to in the UNSC Army and Marine Corps. As the smallest unit, it serves as the base upon which all other units are organized from. The closest organizational unit in the Covenant Army is known as a "Lance."
The concept of the fireteam is based on the need for tactical flexibility in infantry operations. They generally consist of approximately four soldiers or Marines who are formed into a squad. Generally, a squad contains three fireteams.
A fireteam is capable of autonomous operations as part of a larger unit. Successful fire team employment relies on quality small unit training for troops, experience of its members operating together, sufficient communications infrastructure, and a quality non-commissioned officer corps to provide tactical leadership for the team.
Note: The number of troops, their armament, and their roles in the team may vary from team to team. For example some teams may include an anti-matériel specialist, a demolitions expert, a designated marksman, a combat medic, or other mission-critical personnel. In many cases, this specialized function replaces the basic rifleman position in the fireteam. The following is just an example.
- Fireteam Leader (FTM): First in command, provides tactical leadership. A fire team can be lead by a Sergeant in the Army or a Corporal in the Marine Corps, though a Lance Corporal can lead if there is no Cpl. Usually wields an service rifle such as an MA5 assault rifle or a BR55 battle rifle. Generally, the Fireteam Leader will mount an underslung grenade launcher on their rifle.
- Designated Automatic Rifleman (DAR): For added firepower against a large number of enemies or vehicles, this soldier or Marine will carry some type of automatic weapon, such as the M739 SAW or M247 GPMG.
- Rifleman (R): The most common role in a fire team. Several riflemen may be incorporated into a fire team and in some situations is the only member needed. Usually carries Assault Rifle and/or Battle Rifle service weapons, a sidearm, and provides suppressive fire for the team. They are the most common members of a fireteam; they are considered the backbone of operations for the UNSC infantry as a whole, as every other specialists' role exists to augment and support the rifleman's capabilities.
- Additional specialists from each fireteam in a rifle squad is usually one (or more) of the following:
- Assistant Automatic Rifleman (AAR; Marine Corps only): Carries extra ammunition or other weapon-related kit for the designated automatic rifleman in the team; normally carries a service rifle.
- Designated Grenadier (DG; Army only): Unlike the Marine Corps, the Army fireteam has a designated grenadier instead of having the Fireteam Leader operate a grenade launcher underneath his rifle; this soldier or Marine will carry some type of grenade launcher, such as the M319 IGL or "Sticky" Detonator.
- Designated Marksman (DM): The marksman lays down accurate rapid fire at valuable targets as needed, thus extending the reach of the fireteam; this soldier or Marine will carry some type of designated marksman rifle. May also serve as the fireteam's "Scout".
- Anti-Armor Specialist (RMAT): The anti-vehicle specialist; this soldier or Marine will carry some type of rocket launcher, landmines, or an "Anti-Matériel" sniper rifle.
 Notable Fireteams
 Marine Corps
 Special Operations Forces
- An accurate fireteam (Leader, Rifleman, Automatic Rifleman, and Grenadier) hasn't been depicted in any form of Halo media.