Arlington Reservoir is a 100.4-hectare (248-acre) biological Site of Special Scientific Interest west of Hailsham in East Sussex, England.

[1][2] It is also a Local Nature Reserve and it is owned and managed by South East Water.

Alder Alnus glutinosa and willow Salix species are part of the open water.

It is a popular place to view the population of cormorants which regularly visit to rest on the banks and trees surrounding the water.

Other species include great crested grebe, swallow, mallard, pied wagtail, coot, Canada goose, rook, and sheep graze in the surrounding water meadows.