| Country: | Wales |
| Welsh Name: | Pen yr Alltwen |
| Static Image Caption: | Clwb Rygbi Alltwen and the Triangle |
| Constituency Welsh Assembly: | Neath |
| Official Name: | Alltwen |
| Coordinates: | 51.714°N -3.846°W |
| Population: | 2,327 |
| Population Ref: | (2011)[1] |
| Community Wales: | Cilybebyll |
| Unitary Wales: | Neath Port Talbot |
| Lieutenancy Wales: | West Glamorgan |
| Constituency Westminster: | Neath |
| Post Town: | NEATH |
| Postcode District: | SA8 |
| Postcode Area: | SA |
| Dial Code: | 01792 |
| Os Grid Reference: | SN726034 |
Alltwen (or Allt-wen; translates to "white wooded slope") is a village in the Swansea Valley (Welsh: Cwmtawe) in Wales. Alltwen forms part of the community of Cilybebyll and is administered separately from adjoining Pontardawe on the opposite bank of the River Tawe.
Alltwen is served by Alltwen Primary School and the village has a rugby union club, Alltwen RFC (Welsh: Clwb Rygbi Alltwen).
Allt-wen is an electoral ward of Neath Port Talbot county borough and is a part of the community of Cilybebyll. The ward is bounded by Trebanos and Pontardawe to the northwest; Rhos to the northeast; Bryn-côch North to the southeast; Dyffryn to the south; and Clydach (in Swansea) to the southwest.
Most of Allt-wen consists of farmland and woods. Occupying a strip of land in the northwest of the ward is Alltwen village, which is part of the built-up area surrounding Pontardawe.