The Bassac River (commonly called Tonle Bassac ទន្លេបាសាក់) is a distributary of the Tonle Sap and Mekong River. The river starts in Phnom Penh, Cambodia, and flows southerly, crossing the border into Vietnam near Châu Đốc.
In Vietnam, it is known as the Hậu River (Sông Hậu or Hậu Giang in Vietnamese).
The Bassac River is an important transportation corridor between Cambodia and Vietnam, with barges and other crafts plying the waters.
Two bridges span the Bassac: the Monivong Bridge in Phnom Penh, Cambodia and the Can Tho Bridge in Can Tho in Vietnam.