The Eastern Scheldt (Dutch: Oosterschelde) is a former estuary in the province of Zeeland, Netherlands, between Schouwen-Duiveland and Tholen on the north and Noord-Beveland and Zuid-Beveland on the south. It is also the largest national park in the Netherlands, founded in 2002.
During the Roman Era it was the major mouth of the Scheldt River. Before the St. Felix's Flood of 1530, it flowed north as a river from the east end of the Westerschelde, turned west a little west of Bergen op Zoom, and then west along the north edge of what is now the Verdronken Land van Reimerswaal, and after that widened into an estuary. Later parts of that lost land were reclaimed, restricting part of the connection to the Scheldt River to a narrow channel called the Kreekrak, which silted up and became unnavigable. In 1867 the Kreekrak was closed off with a railway embankment, connecting in the process the island of Zuid-Beveland to the mainland of North Brabant. From that moment on, the Oosterschelde lost its connection with the Scheldt, and is no longer functioning as an estuary.
Between Schouwen-Duiveland and Noord-Beveland there are two road connections, the Oosterscheldedam on the west and the Zeeland Bridge on the east.
After the North Sea flood of 1953, it was decided to close off the Oosterschelde by means of a dam and barrier. The Oosterscheldekering (Eastern Scheldt Storm Surge Barrier), between Schouwen-Duiveland and Noord-Beveland, is the largest of 13 ambitious Delta Works designed to protect a large part of the Netherlands from flooding. A four-kilometre section has huge sluice gates, which are normally open but can be closed in adverse weather.