Albemarle Sound is a large estuary on the coast of North Carolina in the United States located at the confluence of a group of rivers, including the Chowan and Roanoke. It is separated from the Atlantic Ocean by the Currituck Banks, a barrier peninsula upon which the town of Kitty Hawk is located, at the eastern edge of the sound, and part of the greater Outer Banks region. Roanoke Island is situated at the southeastern corner of the sound, where it connects to Pamlico Sound. Much of the water in the Albemarle Sound is brackish or fresh, as opposed to the saltwater of the ocean, as a result of river water pouring into the sound.

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.