Rickmansworth is a town in south-west Hertfordshire, England, located approximately 17 miles north-west of central London, 5 miles south-west of Watford and inside the perimeter of the M25 motorway. The town is mainly to the north of the Grand Union Canal and the River Colne. Rickmansworth is the administrative seat of the Three Rivers District Council; the confluence of the River Chess and the River Gade with the Colne in Rickmansworth inspired the district's name.