The Sekong River (, ), is a river in Mainland Southeast Asia and an important tributary of the Mekong river.
The river originates in Huế in Central Vietnam and flows through southern Laos and northeastern Cambodia. It joins the Tonlé San near the Stung Treng town of Cambodia, just 5 miles upstream from the confluence of the Tonlé San and the Mekong river.
Part of its course forms the international boundary between Laos and Cambodia.