Major

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

Covenant

 * Major Grunts; red armored Gruntss
 * Major Brutes; armored Brutes of Halo 2.
 * Major Jackals; orange armored Jackals.
 * Major Elites; red armored Elites.
 * Drone Majors; a Drone rank in Halo 3.

UNSC

 * Major; commissioned officer rank of the UNSC Marine Corps and UNSC Army.
 * Major General; 3rd highest rank in the UNSC Marine Corps and UNSC Army.

Forerunner

 * Sentinel Majors; gold-plated Sentinel constructs with shields.