The Wash is a shallow natural rectangular bay and multiple estuary on the east coast of England in the United Kingdom. It is an inlet of the North Sea and is the largest multiple estuary system in the UK, as well as being the largest natural bay in England and is the outflow for the rivers Witham, Welland, Nene and the Great Ouse. It is also one of the most important places of conservation in Europe, with several nature reserves located within this area.
The coastline is partly in Lincolnshire and partly in Norfolk. The Lincolnshire side forms part of the only coastline of the East Midlands region whilst the Norfolk side forms the north-west corner of the East Anglian region. The coastline stretches from Gibraltar Point just south of the seaside town of Skegness to Gore Point near the village of Holme-next-the-Sea, just east of the seaside town of Hunstanton in Norfolk. These two points are over 75 miles (121 km) from each other by road, but only eleven and a half miles (18.5 km) by sea.
The bay is made up of multiple estuaries, marshland, deep water channels (in particular the Boston and Lynn Deeps), shifting shallow water channels which are all surrounded by multiple sandbanks.
There are several large settlements near its coastline, the largest is the town of King's Lynn in Norfolk followed by the two slightly smaller towns of Boston in Lincolnshire and Wisbech in Cambridgeshire. These are the three main inland ports in the Wash area; a fourth smaller port is also available for shipping on the River Nene at Sutton Bridge and a small marina for pleasure craft is also accessible on the tidal River Welland at Fosdyke Bridge. Nearby, on either side of the Wash at almost opposite ends to each other, are the seaside towns of Skegness which is located on the top of the Lincolnshire side just north of Gibraltar Point and Hunstanton on the top of the Norfolk side north of the nearby royal estate of Sandringham.