London is a city in and the county seat of Madison County, Ohio, United States. Located about 25 miles (40 km) southwest of the Ohio capital of Columbus, London was established in 1811 to serve as the county seat. As of the 2000 census, the city population was 8,771, an increase from 7,807 in 1990. It is the largest community in the United States named London. The ZIP code is 43140. London is served by the London Public Library.