166 (Mixed) Heavy Anti-Aircraft Regiment RA(TA) was formed at Lipson, Plymouth in August 1942 with two batteries. The Regiment was disbanded in May 1945 at Milford Haven, Pembrokeshire.
| Aug 42 | Formed | Plymouth, Devon, UK |
| Aug 42 | 55 Anti-Aircraft Brigade, 8 Anti-Aircraft Division | Plymouth, Devon, UK |
| Aug 43 | 45 Anti-Aircraft Brigade, 3 Anti-Aircraft Group | South West, UK |
| Aug 44 | 61 Anti-Aircraft Brigade | UK |
| May 45 | Disbanded | Pembrokeshire, UK |
Batteries
| Aug 42 | 549 (Mixed), 555 (Mixed) |
| May 43 | 549 (M), 555 (M), 580 (M) |
| Mar 45 | 549 (M), 555 (M) |
