The Ouse is a 35 miles long river in the English counties of West and East Sussex. It rises near Lower Beeding in West Sussex, and flows eastwards and then southwards to reach the sea at Newhaven. It skirts Haywards Heath and passes through Lewes. It forms the main spine of an extensive network of smaller streams, of which the River Uck is the main tributary. As it nears the coast it passes through the Lewes and Laughton Levels, an area of flat, low-lying land that borders the river and another tributary, the Glynde Reach. It was a large tidal inlet at the time of the Domesday book in 1086, but over the following centuries, some attempts were made to reclaim some of the valley floor for agriculture, by building embankments, but the drainage was hampered by the buildup of a large shingle bar which formed across the mouth of the river by longshore drift.

East Sussex is a ceremonial county in South East England. It is bordered by Kent to the north-east, West Sussex to the west, Surrey to the north-west, and the English Channel to the south. The largest settlement is the city of Brighton and Hove, and the county town is Lewes.