| Penwhirn Dam | |
| Location: | Wigtownshire, Dumfries and Galloway, Scotland |
| Pushpin Map: | United Kingdom |
| Agency: | Scottish Water |
| Coordinates: | 54.986°N -4.935°W |
| Inflow: | Penwhirn Burn |
Penwhirn Reservoir, is a reservoir in Dumfries and Galloway, Scotland, approximately 3.5miles east of Cairnryan. The reservoir was built in the 1950s to provide water to the Stranraer area.[1] The reservoir has an associated treatment works located to the east of the dam providing drinking water for a population of around 27,000 people. The dam height was raised in 2015 at cost of £8m to increase the capacity of the reservoir by around 40%.[2] [3]