| Gwarchodfa Natur Genedlaethol Yr Wyddfa | 1672.23 ha | | — |
| Rhinog National Nature Reserve | 682.6 ha | | — |
| Cader Idris National Nature Reserve | 436.92 ha | | — |
| Glynllifon Country Park | 407.07 ha | | — |
| Ceunant Llennyrch National Nature Reserve | 329.46 ha | | — |
| Penrhyn Park | 300.1 ha | | — |
| Morfa Dyffryn National Nature Reserve | 178.37 ha | | — |
| Gwarchodfa Natur Genedlaethol Coedydd Aber | 156.89 ha | | — |
| Gwarchodfa Natur Genedlaethol Cors Geirch | 114.69 ha | | — |
| Gwarchodfa Natur Genedlaethol Hafod Garregog | 86.52 ha | | — |
| Coedydd Maentwrog National Nature Reserve | 68.35 ha | | — |
| Coed Camlyn National Nature Reserve | 63.21 ha | | — |
| Gwarchodfa Natur Genedlaethol Cors Gyfelog | 36.97 ha | | — |
| Coed y Rhygen National Nature Reserve | 27.79 ha | | — |
| Gwarchodfa Natur Genedlaethol Coed Cymerau | 26.32 ha | | — |
| Morfa Madryn | 25.1 ha | | — |
| Coed Ganllwyd National Nature Reserve | 24.37 ha | | — |
| Muriau'r Gwyddelod | 24.0 ha | | — |
| Coed Ganllwyd National Nature Reserve | 19.44 ha | | — |
| Gwarchodfa Natur Genedlaethol Coed Tremadog | 19.36 ha | | — |
| Treborth Botanic Garden | 10.48 ha | | — |
| Forest Holidays Beddgelert Forest Holidays Ltd | 9.33 ha | 🐕 | — |
| Arthog Bog | 7.37 ha | | — |
| Parc Tan-y-Bwlch | 6.86 ha | | — |
| Coed Cynfal National Nature Reserve | 5.45 ha | | — |
| Nant Porth Nature Reserve North Wales Wildlife Trust | 4.43 ha | | — |
| Llyn Celanedd North Wales Wildlife Trust | 3.65 ha | | — |
| University Gardens Park | 3.45 ha | | — |
| Wern Mynach Nature Reserve | 3.11 ha | | — |
| Roman Camp | 2.71 ha | | — |
| Twyni Llandanwg Sand Dunes | 2.25 ha | | — |
| Rhodgadfan Park and Community Woodland | 2.19 ha | | — |
| Aber Artro Hall Gardens | 1.83 ha | | — |
| Bywyd Gwyllt Glaslyn Wildlife Bywyd Gwyllt Glaslyn Wildlife CIC | 1.71 ha | | — |
| Mochras SSSI | 1.68 ha | | — |
| Cae Bryn Coed | 1.34 ha | | — |
| Oakeley Square | 1.12 ha | | — |
| Bangor Park | 0.96 ha | | — |
| Parc Porthmadoc | 0.86 ha | | — |
| Dolgellau Park | 0.7 ha | | — |
| Bangor Park | 0.58 ha | | — |
| Rock Garden | 0.55 ha | | — |
| Walled Kitchen Garden | 0.53 ha | | — |
| Walled Garden National Trust | 0.52 ha | | — |
| Fronheulog | 0.47 ha | | — |
| Victoria Park | 0.29 ha | | — |
| Tywyn Recreation Ground | 0.27 ha | | — |
| Tywyn Sheep Tourist Display | 0.27 ha | | — |
| Tywyn Fruit Tree Conservation Park | 0.24 ha | | — |
| Pendre Park | 0.22 ha | | — |
| Bangor University Healing Garden | 0.21 ha | | — |
| Bible Garden | 0.2 ha | | — |
| Penhelig Park | 0.17 ha | | — |
| Bryn Paderau Memorial Park | 0.15 ha | | — |
| Egryn Abbey | 0.15 ha | | — |
| Llys Dafydd | 0.09 ha | | — |
| Chinese Garden | 0.08 ha | | — |
| Kitchen garden Caban Cafe | 0.06 ha | | — |
| Welsh herbal garden | 0.05 ha | | — |
| William Morris Rose Garden | 0.05 ha | | — |
| Rock garden | 0.03 ha | | — |
| Municipal Garden | 0.02 ha | | — |
| Butterfly border | 0.01 ha | | — |
| Bwyd Bendigedig Port / Incredible Edible Porthmadog | 0.01 ha | | — |
| South African border | 0.01 ha | | — |
| Yr Ardd Fach | 0.01 ha | | — |
| Bog Garden | — | | — |
| Cwins | — | | — |
| Plas Brondanw | — | | — |
| Size of Wales | — | | — |