- The Starfleet Marine Corps Twenty-First Brigade was an element of the Starfleet Marine Corps active in the late 24th century.
- The 21st Brigade consisted of at least one battalion. At some point in the 2370s, the 21st Brigade and its one battalion were subsumed into the Starfleet Marine Corps Ninth Brigade, Second Battalion.
- In the late 1990s, Region 21 (Germany) was absorbed into Region 9 (European Union).
|United Federation of Planets Starfleet Marine Corps brigades|
|1st Bde • 2nd Bde • 4th Bde • 5th Bde • 6th Bde • 7th Bde • 9th Bde • 10th Bde • 11th Bde • 12th Bde • 13th Bde • 15th Bde • 17th Bde • 20th Bde • 21st Bde|