The MA5D Individual Combat Weapon System, known as the MA5D Assault Rifle or simply the Assault Rifle, is a standard-issue rifle of the UNSC Marines.

The MA5D uses an air-cooled, gas-operated, magazine-fed design for fully automatic fire, and is one of the most versatile weapons in the UNSC arsenal. It has been in use for more than 50 years, and can be outfitted with countless attachments, including grenade launchers, suppressors, and flashlights, as well as different ammunition types. The rifle also includes a electronic suite on the back which provides information on rounds remaining, a compass, and several other functions.

Although prized for its close-quarters capabilities, the Assault Rifle has very low and inconsistent accuracy at medium and further ranges. It is recommended, when aiming at more distant targets, to fire in bursts, as this keeps most bullets on point. In close-quarters, firing continuously while moving closer to a target and then killing them with a melee is a powerful tactic against difficult enemies.

The Assault Rifle has been in every Halo game made to date, and will be in the upcoming Halo 5. The MA5D, however, has only been in Halo 4. Earlier games used either the MA5C or MA5B, which are almost identical to the MA5D.