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 peninsulas.
| Island | Area (sq mi) | Area (km2) | ||
|---|---|---|---|---|
| 1 | Anglesey | 260.37 | 674.36 | |
| 2 | Holy Island | 15.22 | 39.44 | |
| 3 | Skomer | 1.12 | 2.90 | |
| 4 | Ramsey Island | 0.99 | 2.58 | |
| 5 | Caldey Island | 0.84 | 2.18 | |
| 6 | Bardsey Island | 0.79 | 2.06 | |
| 7 | Skokholm | 0.41 | 1.06 | |
| 8 | Flat Holm | 0.21 | 0.33 | |
| 9 | Ynys Llanddwyn | 0.19 | 0.3 | |
| 10 | Puffin Island | 0.11 | 0.28 | |
| 11 | Cardigan Island | 0.06 | 0.15 |
There are no islands of any great size in lakes in Wales. The crannog in Llangorse Lake is an artificial island. Several reservoirs contain islets e.g. Llyn Brenig, Elan Valley Reservoirs and Llyn Trawsfynydd, the last named having the largest and most numerous, though some are linked by causeways.
Some places around the Welsh coast are called island or (Welsh) ynys, but are not. Caution is required in that whilst 'ynys' most commonly translates as island, it has other meanings too. Some of these named places were formerly islands surrounded by marshland. Others are peninsulas or just coastal settlements. They include:[2]