21 Anti-Aircraft Z Regiment RA formed in December 1942 at Whitburn Hall, Whitburn with three batteries. It was re-designated in April 1944 at Belle Vue Bank, Low Fell, Gateshead. 21 Anti-Aircraft Z Regiment RA disbanded in March 1945.
| Dec 42 | Formed | Whitburn, Co Durham, UK | |
| Dec 42 |  |
Anti-Aircraft Command | County Durham, UK |
| Apr 43 | |
6 Anti-Aircraft Group, 30 Anti-Aircraft Brigade | North East England |
| Apr 44 | |
5 Anti-Aircraft Group, 30 Anti-Aircraft Brigade | Eastern England |
| Apr 44 | |
Became 21 Anti-Aircraft Area Mixed Regiment | Gateshead, Tyne & Wear, UK |
| Mar 45 | Disbanded |
Batteries
| Dec 42 | 109, 110, 213 |
Batteries manned by Home Guard
| Battery | Home Guard Unit | Date from |
| 110 Battery | 101 Durham (Mixed) | Nov 42 |
| 213 Battery | 101 Northumberland (Mixed) | Nov 42 |