| Silent Valley Reservoir | |
|---|---|
 | |
  Silent Valley Reservoir | |
| Location | County Down, Northern Ireland |
| Coordinates | 54°08′N 6°00′W / 54.133°N 6.000°W |
| Lake type | reservoir |
| Basin countries | United Kingdom, Ireland |
The Silent Valley Reservoir is a reservoir located in the Mourne Mountains near Kilkeel, County Down in Northern Ireland. It supplies most of the water for County Down, surrounding counties and most of Belfast. It is owned and maintained by Northern Ireland Water Limited (formerly DRD Water Service). The reservoir was built between 1923 and 1933 by a workforce of over 1,000 men, nine of whom died during construction.