91 Anti-Aircraft Regiment RA(TA) was formed at Goole, Yorkshire in March 1939. It was re-designated as 91 Heavy Anti-Aircraft Regiment RA(TA) in June 1940. The Regiment was placed in suspended animation in July 1944 and reconstituted as 491 (M) Heavy Anti-Aircraft Regiment RA(TA) in January 1947.
| Mar 39 | 31 Anti-Aircraft Brigade, 7 Anti-Aircraft Division | Hull, Yorkshire, UK |
| May 40 | 39 Anti-Aircraft Brigade, 2 Anti-Aircraft Division | Hull, Yorkshire, UK |
| Jan 41 | 39 Anti-Aircraft Brigade, 10 Anti-Aircraft Division | Hull, Yorkshire, UK |
| Apr 42 | 65 Anti-Aircraft Brigade | Hull, Yorkshire, UK |
| Apr 42 | War Office Reserve | Leeds, Yorkshire, UK |
| Jul 42 | British Troops Egypt | Egypt |
| Sep 42 | 20 Anti-Aircraft Brigade, 9 Army | Beirut, Lebanon |
| Jun 43 | Diluted by African Pioneer Corps men | |
| Sep 43 | 81 Anti-Aircraft Brigade | Haifa, Palestine |
| Jan 44 | Middle East Forces | El Tahag, Egypt |
| Mar 44 | 18 Anti-Aircraft Brigade | Alexandria, Egypt |
| Jul 44 | Suspended animation |
Batteries
| Mar 39 | 221 (1st West Riding), 270 (Wentworth), 286 |
| Mar 41 | 221, 270, 286, 395 |
| Dec 41 | 221, 286, 395, 478 |
| Apr 42 | 221, 286, 395 |
Gun Sites Occupied
Site-*/*=old site/new site
| Dates | Gun Site | Gun Defended Area |
| Sep 39 | J/H9 Stone Creek | Humber |
