| Location | Locality | Coordinates
(links to map & photo sources) | OS grid
reference |
| Cwm | Shropshire | 52°24′N 2°59′W / 52.40°N 02.98°W / 52.40; -02.98 | SO3379 |
| Cwm | Blaenau Gwent | 51°44′N 3°11′W / 51.73°N 03.18°W / 51.73; -03.18 | SO1805 |
| Cwm | Neath Port Talbot | 51°38′N 3°44′W / 51.63°N 03.73°W / 51.63; -03.73 | SS8094 |
| Cwm | Denbighshire | 53°17′N 3°25′W / 53.28°N 03.41°W / 53.28; -03.41 | SJ0677 |
| Cwmafan | Neath Port Talbot | 51°37′N 3°46′W / 51.61°N 03.76°W / 51.61; -03.76 | SS7892 |
| Cwmaman | Rhondda, Cynon, Taff | 51°41′N 3°26′W / 51.68°N 03.44°W / 51.68; -03.44 | ST0099 |
| Cwmann | Carmarthenshire | 52°06′N 4°04′W / 52.10°N 04.07°W / 52.10; -04.07 | SN5847 |
| Cwmavon | Torfaen | 51°44′N 3°03′W / 51.74°N 03.05°W / 51.74; -03.05 | SO2706 |
| Cwmbach | Powys | 52°02′N 3°13′W / 52.04°N 03.22°W / 52.04; -03.22 | SO1639 |
| Cwmbach | Carmarthenshire | 51°53′N 4°32′W / 51.89°N 04.54°W / 51.89; -04.54 | SN2525 |
| Cwmbach | Rhondda, Cynon, Taff | 51°41′N 3°25′W / 51.69°N 03.41°W / 51.69; -03.41 | SO0201 |
| Cwmbach Llechrhyd | Powys | 52°10′N 3°26′W / 52.17°N 03.43°W / 52.17; -03.43 | SO0254 |
| Cwmbelan | Powys | 52°25′N 3°34′W / 52.41°N 03.56°W / 52.41; -03.56 | SN9481 |
| Cwmbran | Torfaen | 51°38′N 3°01′W / 51.64°N 03.02°W / 51.64; -03.02 | ST2995 |
| Cwmbrwyno | Ceredigion | 52°24′N 3°55′W / 52.40°N 03.91°W / 52.40; -03.91 | SN7080 |
| Cwm Capel | Carmarthenshire | 51°41′N 4°14′W / 51.69°N 04.24°W / 51.69; -04.24 | SN4502 |
| Cwmcarn | Caerphilly | 51°38′N 3°08′W / 51.63°N 03.14°W / 51.63; -03.14 | ST2193 |
| Cwmcarvan | Monmouthshire | 51°45′N 2°46′W / 51.75°N 02.76°W / 51.75; -02.76 | SO4707 |
| Cwm-celyn | Blaenau Gwent | 51°46′N 3°10′W / 51.76°N 03.16°W / 51.76; -03.16 | SO2008 |
| Cwmcerdinen | Swansea | 51°44′N 3°59′W / 51.74°N 03.98°W / 51.74; -03.98 | SN6307 |
| Cwm-Cewydd | Gwynedd | 52°42′N 3°40′W / 52.70°N 03.67°W / 52.70; -03.67 | SH8713 |
| Cwmcoednerth | Ceredigion | 52°06′N 4°25′W / 52.10°N 04.42°W / 52.10; -04.42 | SN3448 |
| Cwm-cou | Carmarthenshire | 52°02′N 4°29′W / 52.04°N 04.49°W / 52.04; -04.49 | SN2941 |
| Cwmcrawnon | Powys | 51°52′N 3°15′W / 51.86°N 03.25°W / 51.86; -03.25 | SO1419 |
| Cwmcych | Pembrokeshire | 51°59′N 4°31′W / 51.98°N 04.52°W / 51.98; -04.52 | SN2735 |
| Cwmdare | Rhondda, Cynon, Taff | 51°43′N 3°28′W / 51.71°N 03.47°W / 51.71; -03.47 | SN9803 |
| Cwm Dows | Caerphilly | 51°39′N 3°09′W / 51.65°N 03.15°W / 51.65; -03.15 | ST2096 |
| Cwmdu | Carmarthenshire | 51°57′N 3°59′W / 51.95°N 03.99°W / 51.95; -03.99 | SN6330 |
| Cwmdu | Powys | 51°53′N 3°11′W / 51.89°N 03.19°W / 51.89; -03.19 | SO1823 |
| Cwmdu | Swansea | 51°37′N 3°58′W / 51.62°N 03.96°W / 51.62; -03.96 | SS6494 |
| Cwmduad | Carmarthenshire | 51°57′N 4°22′W / 51.95°N 04.37°W / 51.95; -04.37 | SN3731 |
| Cwm Dulais | Swansea | 51°42′N 4°01′W / 51.70°N 04.01°W / 51.70; -04.01 | SN6103 |
| Cwmdwr | Carmarthenshire | 51°58′N 3°53′W / 51.97°N 03.89°W / 51.97; -03.89 | SN7032 |
| Cwmerfyn | Ceredigion | 52°25′N 3°55′W / 52.42°N 03.92°W / 52.42; -03.92 | SN6982 |
| Cwmfelin | Merthyr Tydfil | 51°41′N 3°19′W / 51.69°N 03.31°W / 51.69; -03.31 | SO0900 |
| Cwmfelin | Bridgend | 51°35′N 3°38′W / 51.58°N 03.64°W / 51.58; -03.64 | SS8689 |
| Cwmfelin Boeth | Carmarthenshire | 51°50′N 4°37′W / 51.84°N 04.62°W / 51.84; -04.62 | SN1919 |
| Cwmfelinfach | Caerphilly | 51°37′N 3°11′W / 51.61°N 03.18°W / 51.61; -03.18 | ST1891 |
| Cwmfelin Mynach | Carmarthenshire | 51°53′N 4°35′W / 51.88°N 04.58°W / 51.88; -04.58 | SN2224 |
| Cwmffrwd | Carmarthenshire | 51°49′N 4°17′W / 51.82°N 04.29°W / 51.82; -04.29 | SN4217 |
| Cwm Ffrwd-oer | Torfaen | 51°42′N 3°04′W / 51.70°N 03.07°W / 51.70; -03.07 | SO2601 |
| Cwm-Fields | Torfaen | 51°41′N 3°02′W / 51.69°N 03.04°W / 51.69; -03.04 | SO2800 |
| Cwm Gelli | Caerphilly | 51°40′N 3°12′W / 51.67°N 03.20°W / 51.67; -03.20 | ST1798 |
| Cwmgiedd | Powys | 51°47′N 3°46′W / 51.78°N 03.77°W / 51.78; -03.77 | SN7811 |
| Cwmgors | Carmarthenshire | 51°46′N 3°53′W / 51.77°N 03.88°W / 51.77; -03.88 | SN7010 |
| Cwmgwili | Carmarthenshire | 51°46′N 4°04′W / 51.77°N 04.07°W / 51.77; -04.07 | SN5710 |
| Cwmgwrach | Neath Port Talbot | 51°43′N 3°39′W / 51.72°N 03.65°W / 51.72; -03.65 | SN8604 |
| Cwm Gwyn | Swansea | 51°37′N 3°59′W / 51.61°N 03.98°W / 51.61; -03.98 | SS6393 |
| Cwm Head | Shropshire | 52°29′N 2°51′W / 52.48°N 02.85°W / 52.48; -02.85 | SO4288 |
| Cwmhiraeth | Carmarthenshire | 52°00′N 4°25′W / 52.00°N 04.42°W / 52.00; -04.42 | SN3437 |
| Cwm-hwnt | Rhondda, Cynon, Taff | 51°44′N 3°34′W / 51.73°N 03.57°W / 51.73; -03.57 | SN9105 |
| Cwmifor | Carmarthenshire | 51°54′N 3°58′W / 51.90°N 03.96°W / 51.90; -03.96 | SN6525 |
| Cwm Irfon | Powys | 52°07′N 3°41′W / 52.12°N 03.68°W / 52.12; -03.68 | SN8549 |
| Cwmisfael | Carmarthenshire | 51°49′N 4°11′W / 51.81°N 04.19°W / 51.81; -04.19 | SN4915 |
| Cwm-Llinau | Powys | 52°38′N 3°43′W / 52.64°N 03.71°W / 52.64; -03.71 | SH8407 |
| Cwmllynfell | Neath Port Talbot | 51°47′N 3°49′W / 51.79°N 03.82°W / 51.79; -03.82 | SN7412 |
| Cwm-mawr | Carmarthenshire | 51°47′N 4°08′W / 51.78°N 04.13°W / 51.78; -04.13 | SN5312 |
| Cwm-miles | Carmarthenshire | 51°52′N 4°40′W / 51.86°N 04.67°W / 51.86; -04.67 | SN1622 |
| Cwm Nant-gam | Blaenau Gwent | 51°48′N 3°10′W / 51.80°N 03.16°W / 51.80; -03.16 | SO2012 |
| Cwmnantyrodyn | Caerphilly | 51°38′N 3°11′W / 51.64°N 03.18°W / 51.64; -03.18 | ST1895 |
| Cwmorgan | Pembrokeshire | 51°58′N 4°29′W / 51.97°N 04.49°W / 51.97; -04.49 | SN2934 |
| Cwmparc | Rhondda, Cynon, Taff | 51°39′N 3°31′W / 51.65°N 03.51°W / 51.65; -03.51 | SS9596 |
| Cwmpengraig | Carmarthenshire | 51°59′N 4°25′W / 51.99°N 04.41°W / 51.99; -04.41 | SN3436 |
| Cwm Penmachno | Conwy | 53°00′N 3°52′W / 53.00°N 03.86°W / 53.00; -03.86 | SH7547 |
| Cwmpennar | Rhondda, Cynon, Taff | 51°41′N 3°24′W / 51.69°N 03.40°W / 51.69; -03.40 | SO0300 |
| Cwm Plysgog | Pembrokeshire | 52°03′N 4°38′W / 52.05°N 04.64°W / 52.05; -04.64 | SN1943 |
| Cwmrhos | Powys | 51°54′N 3°11′W / 51.90°N 03.19°W / 51.90; -03.19 | SO1824 |
| Cwmrhydyceirw | Swansea | 51°40′N 3°56′W / 51.67°N 03.93°W / 51.67; -03.93 | SS6699 |
| Cwmsyfiog | Caerphilly | 51°43′N 3°14′W / 51.71°N 03.23°W / 51.71; -03.23 | SO1502 |
| Cwmsymlog | Ceredigion | 52°25′N 3°55′W / 52.42°N 03.91°W / 52.42; -03.91 | SN7083 |
| Cwmtillery | Blaenau Gwent | 51°44′N 3°08′W / 51.73°N 03.14°W / 51.73; -03.14 | SO2105 |
| Cwm-twrch Isaf | Neath Port Talbot | 51°46′N 3°47′W / 51.77°N 03.79°W / 51.77; -03.79 | SN7610 |
| Cwm-twrch Uchaf | Neath Port Talbot | 51°47′N 3°49′W / 51.78°N 03.81°W / 51.78; -03.81 | SN7511 |
| Cwmwdig Water | Pembrokeshire | 51°55′N 5°12′W / 51.92°N 05.20°W / 51.92; -05.20 | SM8030 |
| Cwmwysg | Powys | 51°56′N 3°40′W / 51.93°N 03.67°W / 51.93; -03.67 | SN8528 |
| Cwm-y-glo | Gwynedd | 53°08′N 4°10′W / 53.13°N 04.16°W / 53.13; -04.16 | SH5562 |
| Cwmynyscoy | Torfaen | 51°41′N 3°02′W / 51.68°N 03.04°W / 51.68; -03.04 | ST2899 |
| Cwmyoy | Monmouthshire | 51°54′N 3°02′W / 51.90°N 03.03°W / 51.90; -03.03 | SO2923 |
| Cwmystwyth | Ceredigion | 52°21′N 3°47′W / 52.35°N 03.79°W / 52.35; -03.79 | SN7874 |
| Cwrt | Gwynedd | 52°35′N 3°56′W / 52.58°N 03.94°W / 52.58; -03.94 | SH6800 |
| Cwrtnewydd | Ceredigion | 52°06′N 4°13′W / 52.10°N 04.22°W / 52.10; -04.22 | SN4847 |
| Cwrt-y-cadno | Carmarthenshire | 52°04′N 3°55′W / 52.07°N 03.91°W / 52.07; -03.91 | SN6944 |
