Castleshaw
Bleak Hey Nook Lane, Castleshaw
Castleshaw Location within Greater Manchester
OS grid reference	SE000096
Civil parish	Saddleworth
Metropolitan borough	Oldham
Metropolitan county	Greater Manchester
Region	North West
Country	England
Sovereign state	United Kingdom
Post town	OLDHAM
Postcode district	OL3
Dialling code	01457
Police	Greater Manchester
Fire	Greater Manchester
Ambulance	North West
UK Parliament	Oldham East and Saddleworth
List of places UK England Greater Manchester 53°34′59″N 1°59′56″W / 53.583°N 1.999°W / 53.583; -1.999

Castleshaw is a hamlet in the Saddleworth parish of the Metropolitan Borough of Oldham in Greater Manchester, England.^[1] It lies amid the Pennines, 2.4 miles (3.9 km) north of Uppermill, 3 miles (4.8 km) west-southwest of Marsden, and 5.3 miles (8.5 km) east-northeast of Oldham.

Historically a part of the West Riding of Yorkshire, Castleshaw is most notable for the Castleshaw Roman fort, the remains of an ancient castrum. There are two reservoirs, Castleshaw upper reservoir and Castleshaw lower reservoir. In 2016, United Utilities reinforced the walls on the lower reservoir but had to drop water levels by 1m.

There used to be a Roman fort situated near to the head of the valley. A series of modern mounds and ditches have been laid out to mark the site, on the edge of Castleshaw Upper Reservoir. The Castleshaw area was once also home to a sanitorium, which is now used as a Youth Training Centre.