Grassholme Reservoir is a large reservoir in County Durham, England.

It is situated in Lunedale, which is a side valley of the River Tees, about 2 miles (3.2 km) south of Middleton-in-Teesdale.

It supplies water for Teesdale and Teesside and is owned by Northumbrian Water.

Its main recreational use is as an angling centre.

This County Durham location article is a stub.