Rickmansworth, town (1991 pop. 29,408), Hertfordshire, SE England, at the confluence of the Colne, Gade, and Chess rivers. Rickmansworth is an old market town. The district is largely residential and has many recreation spots, including woods, lakes, and Moor Park (400 acres/162 hectares). Papermaking is a major industry. Basing House, a home of William Penn, is in the vicinity.