| Claerwen National Nature Reserve | 793.7 ha | | — |
| Craig Cerrig Gleisiad a Fan Frynych National Nature Reserve | 489.8 ha | | — |
| Powis Castle Parks | 265.21 ha | | — |
| Gregynog National Nature Reserve | 218.06 ha | | — |
| Talybont Reservoir Nature Reserve | 193.34 ha | | — |
| Nant Irfon National Nature Reserve | 138.41 ha | | — |
| Daudraeth Illtyd Nature Reserve | 91.29 ha | | — |
| Rhos Goch National Nature Reserve | 45.24 ha | | — |
| Ystradfawr Nature Reserve | 39.67 ha | | — |
| Mynydd Ffoesidoes Nature Reserve Radnorshire Wildlife Trust | 35.36 ha | | — |
| Roundton Hill National Nature Reserve | 33.47 ha | | — |
| Cors y Llyn National Nature Reserve | 25.14 ha | | — |
| Pwll y Wrach Nature Reserve Brecknock Wildlife Trust | 16.99 ha | | — |
| Cors Dyfi Nature Reserve Montgomery Wildlife Trust | 16.96 ha | | — |
| Craig-y-nos Country Park | 13.21 ha | | — |
| Burfa Bog | 9.5 ha | | — |
| Dolerw Park | 9.25 ha | 🐕 | — |
| Llyn Coed y Dinas Montgomeryshire Wildlife Trust | 8.05 ha | | — |
| Bailey Einion | 7.53 ha | | — |
| Trehafren Fields | 7.24 ha | | — |
| Wern Plemys Nature Reserve The Wildlife Trust of West and South Wales | 6.26 ha | | — |
| Dan-Yr-Ogof Farm | 6.02 ha | | — |
| The Promenade | 5.51 ha | | — |
| Stanner Rocks National Nature Reserve | 5.4 ha | | — |
| Went’s Meadow | 4.71 ha | | — |
| Site of Hay Festival | 4.53 ha | | — |
| Vaynor Field | 4.27 ha | | — |
| Cui Parc | 3.62 ha | | — |
| Buckland Hall Gardens Buckland Hall | 3.51 ha | | — |
| Sculpture Garden | 3.0 ha | | — |
| Wern Ddu | 2.92 ha | | — |
| Vaynor Fields | 2.84 ha | | — |
| Glasbury Cutting Nature Reserve | 2.21 ha | | — |
| Diamond Park | 1.81 ha | | — |
| Cae Bodfach | 1.8 ha | | — |
| Fairfield | 1.8 ha | | — |
| St David's Field | 1.78 ha | | — |
| Penmyarth | 1.77 ha | | — |
| Gliffaes | 1.6 ha | | — |
| Eligro Nature Reserve | 1.37 ha | | — |
| The Groves | 1.26 ha | | — |
| Severn Farm Pond | 1.25 ha | | — |
| Treowen Field And Primay School | 1.09 ha | | — |
| Brook Street Secret Walled Garden Hay Warren Trust | 0.08 ha | 🐕 | — |
| Gilfach Nature Reserve Radnorshire Wildlife Trust | — | | — |
| Protected Species | — | | — |