Mersey Class Lifeboat 12007 Photograph By Robert Kilpin

The River Mersey () is in North West England. Its name derives from Old English and means "boundary river", possibly referring to its having been a border between the ancient kingdoms of Mercia and Northumbria. For centuries it has formed part of the boundary between the historic counties of Lancashire and Cheshire.

The Mersey starts at the confluence of the River Tame and River Goyt in Stockport. It flows westwards through south Manchester, then into the Manchester Ship Canal at Irlam, becoming a part of the canal and maintaining its water levels. After it exits the canal, flowing towards Warrington where it widens. It then narrows as it passes between Runcorn and Widnes. From Runcorn the river widens into a large estuary, which is across at its widest point near Ellesmere Port. The course of the river then turns northwards as the estuary narrows between Liverpool and Birkenhead on the Wirral Peninsula to the west, and empties into Liverpool Bay. In total the river flows .

A railway tunnel between Birkenhead and Liverpool as part of the Mersey Railway opened in 1886. Two road tunnels pass under the estuary from Liverpool: the Queensway Tunnel opened in 1934 connecting the city to Birkenhead, and the Kingsway Tunnel, opened in 1971, to Wallasey. A road bridge, completed in 1961 and later named the Silver Jubilee Bridge, crosses between Runcorn and Widnes, adjacent to the Runcorn Railway Bridge which opened in 1868. A second road bridge, the Mersey Gateway, opened in October 2017, carrying a six-lane road connecting Runcorn's Central Expressway with Speke Road and Queensway in Widnes. The Mersey Ferry operates between Pier Head in Liverpool and Woodside in Birkenhead and Seacombe, and has become a tourist attraction offering cruises that provide an overview of the river and surrounding areas.

Water quality in the Mersey was severely affected by industrialisation, and in 1985, the Mersey Basin Campaign was established to improve water quality and encourage waterside regeneration. In 2009 it was announced that the river is "cleaner than at any time since the industrial revolution" and is "now considered one of the cleanest in the UK". The Mersey Valley Countryside Warden Service manages local nature reserves such as Chorlton Ees and Sale Water Park.

The river gave its name to Merseybeat, developed by bands from Liverpool, notably the Beatles. In 1965 it was the subject of the top-ten hit single " Ferry Cross the Mersey" by Gerry and the Pacemakers.

Etymology

Its name is derived from the Anglo-Saxon , 'of a boundary' and , 'a river'. The Mersey was possibly the 'border river' between Mercia and Northumbria. Its Welsh name is .

Course

The Mersey is formed from three tributaries: the River Etherow, the River Goyt and the River Tame. The modern accepted start of the Mersey is at the confluence of the Tame and Goyt, in central Stockport, Greater Manchester. However, older definitions, and many older maps, place its start a few miles up the Goyt at Compstall; for example the 1911 Encyclopædia Britannica states "It is formed by the junction of the Goyt and the Etherow a short distance below Marple in Cheshire on the first-named stream." The 1784 John Stockdale map shows the River Mersey extending to Mottram, and forming the boundary between Cheshire and Derbyshire. In the west of Stockport it flows at the base of a cliff below the road called Brinksway before reaching flat country. An early Ordnance Survey map indicates the spring at Red Hole on the Lancashire/Yorkshire boundary at the head of one of the Etherow's longest headwaters, as being the ''Source of the River Mersey''.

Stockport to Warrington

From Central Stockport the river flows through or past Heaton Mersey, Didsbury, Northenden, Chorlton-cum-Hardy, Stretford, Sale, Ashton on Mersey, Urmston and Flixton, then at Irlam flows into the Manchester Ship Canal, which is the canalised section of the River Irwell at this point. The old course of the Mersey has been obliterated by the canal past Hollins Green to Rixton although the old river bed can be seen outside Irlam and at Warburton. At Rixton the River Bollin enters the canal from the south and the Mersey leaves the canal to the north, meandering through Woolston, where the ship canal company's dredgings have formed the Woolston Eyes nature reserve, and on to Warrington. The river is tidal from Howley Weir in Warrington, although high spring tides often top the weir. Before construction of the ship canal, work to improve navigation included Woolston New Cut, bypassing a meander, and Howley Lock for craft to avoid the weir; the new cut and lock are still evident. The island formed between the weir and the lock is known locally as "Monkey Island".

Runcorn Gap

West of Warrington the river widens, and then narrows as it passes through the Runcorn Gap between the towns of Runcorn and Widnes, in Halton. The Manchester Ship Canal passes through the gap to the south of the river. The gap is bridged by the Silver Jubilee Bridge and Runcorn Railway Bridge. Another crossing, the Mersey Gateway road bridge opened in October 2017, and is situated about 1 mile upstream from the Runcorn Gap where the river is considerably wider.

Estuary

From the Runcorn Gap, the river widens into a large estuary, which is wide at its widest point near Ellesmere Port. The course of the river then heads north, with Liverpool to the east and the Wirral Peninsula to the west. The Manchester Ship Canal enters the river at Eastham Locks. The eastern part of the estuary is much affected by silting, and part of it is marked on modern maps as dry land rather than tidal. The wetlands are of importance to wildlife, and are listed as a Ramsar site