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.