| Country: | Wales |
| Official Name: | Pentre-bach |
| Welsh Name: | Pentre-bach |
| Unitary Wales: | Powys |
| Lieutenancy Wales: | Powys |
| Constituency Westminster: | Brecon and Radnorshire |
| Constituency Welsh Assembly: | Brecon and Radnorshire |
| Postcode Area: | LD |
| Postcode District: | LD3 |
| Post Town: | Brecon |
| Coordinates: | 51.9854°N -3.5903°W |
Pentre-bach (Welsh for "small village") is a hamlet (one of several in Wales with similar names) in Powys, Wales,[1] in the former county and current Shire Committee Area of Breconshire or Brecknockshire. It is located on the Afon Cilieni, a small tributary of the River Usk, between Brecon and Llandovery. The hamlet has a pub called the "Shoemakers Arms"[2] or Tafarn y Crydd, and a former chapel, originally Calvinistic Methodist, named "Beili-du",[3] Welsh for "black yard". The nearest church is in Llandeilo'r-Fan, 2 km to the NW, and the nearest shop is in Sennybridge, 4 km to the south.
Construction started of a railway line up the Cilieni valley, but was abandoned in 1867. (See Neath and Brecon Railway and.[4])