| Piethorne Reservoir | |
|---|---|
 | |
  Piethorne Reservoir | |
| Location | Rochdale, Greater Manchester, England |
| Coordinates | 53°36′35″N 2°3′18″W / 53.60972°N 2.05500°W |
| Type | reservoir |
| Primary inflows | Piethorne Brook Cold Greave Brook |
| Primary outflows | Piethorne Brook |
| Basin countries | United Kingdom |
| Max. depth | 22 m (72 ft) |
| Water volume | 344 million imperial gallons (1,270 acre⋅ft) |
Piethorne Reservoir is the largest of several reservoirs in the Piethorne Valley above Newhey, by Milnrow, in the Metropolitan Borough of Rochdale, Greater Manchester, England. It was built between 1858 and 1868.
During excavations at Piethorne in the mid-19th century, a Celtic spear-head with a 5-inch (130 mm) blade was unearthed, implying human habitation in the locality during the Bronze Age.