A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot transport away the supplied sediment.

The Delta River is an tributary of the Tanana River in the U.S. state of Alaska. Its name in the Ahtna language is Saas Na’ . Fed by the Tangle Lakes of the Alaska Range, the river flows north to meet the larger river near Big Delta.