Littlehampton is a town, seaside resort and pleasure harbour, and the most populous civil parish in the Arun District of West Sussex, England. It lies on the English Channel on the eastern bank of the mouth of the River Arun. It is 51.5 miles south south-west of London, 19 miles west of Brighton and 10 miles east of the county town of Chichester.
The parish covers an area of 11.35 km². The suburban area of the town has a population of approximately 55,000. The conurbation includes other settlements: Wick in the north west; Lyminster to the north; and Rustington to the east. Wick and Toddington, which has a large business park, became part of the town in 1901. Nearby towns include Bognor Regis and Worthing to the east.
The town is also the westernmost settlement of the 15th largest urban area in England and Wales, the Brighton/Worthing/Littlehampton conurbation, a region encompassing 474,485 people. The South Downs National Park commences 3 miles north of the town: Littlehampton links to Amberley and Arundel by footpaths and railway as well as by roads.