Coordinates: 51°38′18″N 0°27′57″W / 51.6383°N 0.4659°W / 51.6383; -0.4659
Rickmansworth is a small town in south-west Hertfordshire, England, situated approximately 20 miles (32 km) northwest of central London and inside the perimeter of the M25 motorway. The town is mainly to the north of the Grand Union Canal (formerly the Grand Junction Canal) and the River Colne. The nearest large town is Watford, approximately 5 miles (8.0 km) to the east. Rickmansworth is the administrative seat of the Three Rivers District Council, the local authority named from the confluence of three rivers within its borders. The River Gade and the Grand Union Canal join the upper River Colne near Rickmansworth's eastern boundary and are joined by the River Chess near the town centre from where the enlarged Colne flows south to form a major tributary of the River Thames.
The name Rickmansworth comes from the Saxon name Ryckmer, the local landowner, and worth meaning a farm or stockade. In the Domesday Book of 1086 it was recorded as the Manor of Prichemaresworde. Other spellings include Rykemarwurthe (1119–46), Richemaresworthe (1180), Rykemerewrthe (1248), Richemereworthe (1259), Rikesmareswrth (1287), Rikmansworth (1382), Rikmeresworth (1396) & Rykemerysworth (1418).