Runcorn is an industrial town and cargo port within the borough of Halton in the ceremonial county of Cheshire, England. In mid-2004 its population was estimated to be 61,252. The town is on the southern bank of the River Mersey where the estuary narrows to form Runcorn Gap. Directly to the north across the Mersey is the town of Widnes. Upstream and to the northeast is the town of Warrington, and downstream to the west is the city of Liverpool.

Runcorn railway station is on the West Coast Main Line. It provides frequent services to London (Euston), Liverpool, and Birmingham. The A533 road passes through the town from the south, crossing the Runcorn Gap over the Silver Jubilee Bridge, the lowest bridge crossing of the River Mersey. The Manchester Ship Canal runs between the town and the River Mersey, and the Bridgewater Canal passes through and ends in the town at its junction with the Manchester Ship Canal.

Runcorn was a small, isolated village until the coming of the Industrial Revolution. In the late 18th and early 19th centuries it was a health resort. Towards the end of the 18th century, a port began to develop on the south bank of the River Mersey. During the 19th century industries developed, in particular the manufacture of soap and alkali, quarrying, shipbuilding, engineering, and tanning. In the early 20th century, the prime industries were chemicals and tanning. The original village has grown to include what were outlying villages. Except for chemicals, all the old industries have disappeared, and there has been diversification, in particular because of the close links to the motorway system, and the development of warehousing and distribution centres. A new town was built to the east of the existing town in the 1960s and 1970s, and farther to the east, areas of private housing have been established; this has resulted in a doubling of the population from around 30,000 to its present level.