River Yei is a river in South Sudan with its source in Panyana Village, Lujule payam in Morobo County of Central Equatoria State.

[1] The name Yei was derived from the word yii in Kaliko language, meaning "water.

The river flows through Yei town where the Kembe River joins along Yei - Juba Road.

[3][4] Aga fall is on River Yei located in wudabi Payam of Morobo County in Central Equatoria State In Western Equatoria, the river flows through Mundiri west, Lake State, and Unity State.

In 2011 the government of Central Equatoria State under the leadership of Governor Clement Wani Konga planned to launch a power plant in Morobo County.