21 Anti-Aircraft Brigade was formed in the UK and went to Egypt by January 1943. It served in Egypt until mid 1944. 21 Anti-Aircraft Brigade was disbanded in July 1944.
Illustrations of the formation badges under which a unit served or supported are given. This is no guarantee that the unit used this formations badge.
| Jan 43 | Raised in UK, went to Egypt
Port Said, Suez & Canal, Cairo |  | 8 Army |
| May 43 | Suez Canal, Cairo, Suez |  | GHQ Middle East |
| Jan 44 | In reserve for training | | GHQ Middle East |
| Jun 44 | In concentration pending disbandment | | GHQ Middle East |
| Jul 44 | Disbanded | | |
Order of Battle January 1943
| 2 Heavy Anti-Aircraft Regiment (16, 20 Batteries) |
| 81 Heavy Anti-Aircraft Regiment (253, 254, 255 Batteries) |
| 96 Heavy Anti-Aircraft Regiment (186, 295 Batteries) |
| 5 Heavy Anti-Aircraft Battery Royal Marines |
| 638 Heavy Anti-Aircraft Battery |
| 135 Z Battery |
| 1 Light Anti-Aircraft Regiment (2, 3, 4 Batteries) |
| 38 Light Anti-Aircraft Regiment (51, 124, 125 Batteries) |
| 61 Light Anti-Aircraft Regiment (43, 197 Batteries) |
| 86 Light Anti-Aircraft Regiment (119, 281, 452 Batteries) |
| 38/13 Light Anti-Aircraft Battery |
| 133/41 Light Anti-Aircraft Battery |
| 100/52 Light Anti-Aircraft Battery |
| 27 Searchlight Regiment (304, 305 Batteries) |
| 11 Searchlight Regiment (R, S Batteries) Royal Marines |
Order of Battle May 1943
| 2 Heavy Anti-Aircraft Regiment |
| 81 Heavy Anti-Aircraft Regiment |
| 96 Heavy Anti-Aircraft Regiment |
| 135 Z Battery less one Troop |
| 1 Light Anti-Aircraft Regiment |
| 61 Light Anti-Aircraft Regiment |
| 27 Searchlight Regiment HQ |
| 305 Searchlight Battery |
| 24 Searchlight Battery Hong Kong Singapore RA |
| Royal Marines Searchlight Batteries |
Order of Battle January 1944
| 81 Heavy Anti-Aircraft Regiment |
| 91 Heavy Anti-Aircraft Regiment |
| 191 Heavy Anti-Aircraft Regiment |
| 30 Light Anti-Aircraft Regiment |
Order of Battle June 1944
| 81 Heavy Anti-Aircraft Regiment |
| 193 Heavy Anti-Aircraft Regiment |
| 30 Light Anti-Aircraft Regiment |
| 80 Light Anti-Aircraft Regiment |
