559 Coast Regiment RA was formed as 21 Coast Artillery Group RA at Mumbles with three batteries, in October 1940. It was re-designated 559 Coast Regiment RA in June 1941. RHQ was disbanded in April 1944 and the batteries joined 570 Coast Regiment RA.
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.
| Oct 40 | Formed as 21 Coast Artillery Group | Mumbles, Swansea, UK | |
| Oct 40 |  |
Western Command | Mumbles, Swansea, UK |
| Jun 41 | Became 559 Coast Regiment | Mumbles, Swansea, UK | |
| Dec 42 | Mumbles Fire Command | Mumbles, Swansea, UK | |
| Apr 44 | Disbanded |
Batteries
| Oct 40 | 401 (Port Talbot), 402 (Llanelli), B/531 (Mumbles Hill) |
| Mar 41 | 166 (Mumbles Rock), 401, 402, B/531 |
| Apr 41 | 166, 298 (Mumbles Hill), 401, 402 |
| May 41 | 146, 166, 298, 401, 402 |
| Jun 41 | 146, 298, 401, 402 |
| Dec 41 | 146, 298, 401, 402, 431 – 32 & 33 Coast Observer Detachments |
| May 42 | 146, 299 (Mumbles Hill), 401, 431 – 32 & 33 Coast Observer Detachments |
| Nov 42 | 146, 299, 422, 431 – 32 & 33 Coast Observer Detachments |
| Dec 42 | 299, 422, 431 – 33 Coast Observer Detachment |
| Jul 43 | 299, 422, 431 – 24 & 33 Coast Observer Detachments |