This is a list of islands of Wales, the mainland of which is part of Great Britain, as well as a table of the largest Welsh islands by area. The list includes tidal islands such as Sully Island but not locations such as Shell Island which, though they are termed islands, are in fact peninsulas.
| Island | Area (sq mi) | Area (km²) | |
| 1 | Anglesey | 275.60 | 713.80 |
| 2 | Holy Island | 15.22 | 39.44 |
| 3 | Skomer Island | 1.12 | 2.90 |
| 4 | Ramsey Island | 0.99 | 2.58 |
| 5 | Caldey Island | 0.84 | 2.18 |
| 6 | Bardsey Island | 0.76 | 1.99 |
| 7 | Skokholm | 0.41 | 1.06 |
| 8 | Flat Holm | 0.13 | 0.33 |
| 9 | Puffin Island | 0.11 | 0.28 |
| 10 | Cardigan Island | 0.06 | 0.15 |
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