Major

Major is a common rank both in the Covenant and the UNSC. "Major" may refer to...

Covenant

 * Major Grunts, the red armored Grunts.
 * Major Brutes, the armored Brutes of Halo 2.
 * Major Jackals, the orange armored Jackals.
 * Major Elites, the red armored Elites.

UNSC

 * Major, a junior commissioned officer rank of the UNSC Marine Corps.
 * Major General, the 3rd highest rank in the UNSC Marine Corps.

Forerunner

 * Sentinel Majors, the gold-plated Sentinel constructs.