| Name | Locality | Local Authority | Administrative area |
| Ysbryd-y-coed | Newcastle Higher | Pen-y-bont ar Ogwr / Bridgend | Pen-y-bont Ar Ogwr / Bridgend |
| Ysgol Place | Upper Cwmbran | Tor-faen / Torfaen | Tor-faen / Torfaen |
| Ysgol Street | St. Thomas | Abertawe / Swansea | Abertawe / Swansea |
| Ysgoldy Hill | Ruabon | Wrecsam / Wrexham | Wrecsam / Wrexham |
| Ysgubor | Glantwymyn | Powys / Powys | Powys / Powys |
| Ysgubor Fach | Bedwas, Trethomas and Machen | Caerffili / Caerphilly | Caerffili / Caerphilly |
| Ysgubor Fach Street | Castle | Abertawe / Swansea | Abertawe / Swansea |
| Ysgubor Newydd Lane | Tremeirchion | Sir Ddinbych / Denbighshire | Sir Ddinbych / Denbighshire |
| Ysguboriau'r Bugail | Welshpool | Powys / Powys | Powys / Powys |
| Ysguborwen | Abergavenny | Sir Fynwy / Monmouthshire | Sir Fynwy / Monmouthshire |
| Ysguborwen Road | Penmaenmawr | Conwy / Conwy | Conwy / Conwy |
| Ysguthan Road | Aberavon | Castell-nedd Port Talbot / Neath Port Talbot | Castell-nedd Port Talbot / Neath Port Talbot |
| Yspitty Road | Llanelli Rural | Sir Gaerfyrddin / Carmarthenshire | Sir Gaerfyrddin / Carmarthenshire |
| Yspitty Road | Llanelli Rural | Sir Gaerfyrddin / Carmarthenshire | Sir Gaerfyrddin / Carmarthenshire |
| Yspytty Road | Bro Machno | Conwy / Conwy | Conwy / Conwy |
| Ystad Cae Bach | Bala | Gwynedd / Gwynedd | Gwynedd / Gwynedd |
| Ystad Celyn | Maesteg | Pen-y-bont ar Ogwr / Bridgend | Pen-y-bont Ar Ogwr / Bridgend |
| Ystad Ddiwydiannol Y Glyn | Llanberis | Gwynedd / Gwynedd | Gwynedd / Gwynedd |
| Ystad Deri | Tredegar | Blaenau Gwent / Blaenau Gwent | Blaenau Gwent / Blaenau Gwent |
| Ystad Glorian | Amlwch | Sir Ynys Mon / Isle of Anglesey | Sir Ynys Mon / Isle of Anglesey |
| Ystad Gwylfa | Amlwch | Sir Ynys Mon / Isle of Anglesey | Sir Ynys Mon / Isle of Anglesey |
| Ystad Mur Poeth | Llanengan | Gwynedd / Gwynedd | Gwynedd / Gwynedd |
| Ystad Ty'n Berllan | Bryngwran | Sir Ynys Mon / Isle of Anglesey | Sir Ynys Mon / Isle of Anglesey |
| Ystad-y-gotrel | Cardigan | Sir Ceredigion / Ceredigion | Sir Ceredigion / Ceredigion |
| Ysticl-garu | Llandow | Bro Morgannwg / the Vale of Glamorgan | Bro Morgannwg / The Vale of Glamorgan |
| Ysticlau Road | Seven Sisters | Castell-nedd Port Talbot / Neath Port Talbot | Castell-nedd Port Talbot / Neath Port Talbot |
| Ystrad Close | Carmarthen | Sir Gaerfyrddin / Carmarthenshire | Sir Gaerfyrddin / Carmarthenshire |
| Ystrad Close | Trowbridge | Caerdydd / Cardiff | Caerdydd / Cardiff |
| Ystrad Drive | Carmarthen | Sir Gaerfyrddin / Carmarthenshire | Sir Gaerfyrddin / Carmarthenshire |
| Ystrad Einon | Llwchwr | Abertawe / Swansea | Abertawe / Swansea |
| Ystrad Fawr | Bridgend | Pen-y-bont ar Ogwr / Bridgend | Pen-y-bont Ar Ogwr / Bridgend |
| Ystrad Hir | Trefeglwys | Powys / Powys | Powys / Powys |
| Ystrad Road | Ystrad | Rhondda Cynon Taf / Rhondda Cynon Taf | Rhondda Cynon Taf / Rhondda Cynon Taf |
| Ystrad Road | Cockett | Abertawe / Swansea | Abertawe / Swansea |
| Ystrad Road | Denbigh | Sir Ddinbych / Denbighshire | Sir Ddinbych / Denbighshire |
| Ystrad Road | Pentre | Rhondda Cynon Taf / Rhondda Cynon Taf | Rhondda Cynon Taf / Rhondda Cynon Taf |
| Ystrad Road | Ystrad | Rhondda Cynon Taf / Rhondda Cynon Taf | Rhondda Cynon Taf / Rhondda Cynon Taf |
| Ystrad Road | Pentre | Rhondda Cynon Taf / Rhondda Cynon Taf | Rhondda Cynon Taf / Rhondda Cynon Taf |
| Ystrad Street | Grangetown | Caerdydd / Cardiff | Caerdydd / Cardiff |
| Ystrad Terrace | Ystrad | Rhondda Cynon Taf / Rhondda Cynon Taf | Rhondda Cynon Taf / Rhondda Cynon Taf |
| Ystrad Terrace | Abercarn | Caerffili / Caerphilly | Caerffili / Caerphilly |
| Ystrad-fawr Villas | Ystradgynlais | Powys / Powys | Powys / Powys |
| Ystryd Ddu | Pen-y-bont-Fawr | Powys / Powys | Powys / Powys |
| Ystryd Faen | Trawsfynydd | Gwynedd / Gwynedd | Gwynedd / Gwynedd |
| Ystryd Y Ceunant | Llanfechain | Powys / Powys | Powys / Powys |
| Ystryd Y Ceunant | Llansantffraid | Powys / Powys | Powys / Powys |
| Ystwyth Place | Mynyddbach | Abertawe / Swansea | Abertawe / Swansea |
