The Colne Valley Waterworks railway was a 2 ft (610 mm) narrow gauge industrial railway connecting the London, Midland and Scottish Railway (LMS) Watford to Rickmansworth branch line with the Eastbury Pumping Station to deliver coal.

The Colne Valley Water Company opened the Eastbury Pumping Station near Watford in 1873.

The line ran southeast from a private siding on the LMS line, crossed the River Colne by a relatively substantial plate girder bridge and ended in a yard at the pumping station.

The railway carried coal to power the pumping station and chlorine and salt for the water softening plant.

The pumping station switched from coal to diesel power in 1956; after this use of the railway declined significantly.