district, administrative and historic county of Surrey, England. The River Mole, from which the district takes its name, flows northward across it to join the Thames at Hampton Court, west of London; the river cuts through a line of chalk hills (the North Downs) in a steep-sided valley that is followed by road and rail routes. South of the Downs is a narrow lowland and then a second line of sandstone heights.

From the northern end of the district, near Leatherhead, the built-up area is virtually continuous to central London, but the North Downs and other parts of the district fall within London's Greenbelt or are designated Areas of Outstanding Natural Beauty, thereby enjoying protection from residential development. A considerable number of the district's residents are commuters to the London area.

The town of Dorking stands at the point where the River Mole enters its narrow valley section from the south, and it is the service centre of the district. Area 100 square miles (259 square km). Pop. (2001) 80,294.