Ban Gioc – Detian Falls (Vietnamese: thác Bản Giốc, Chinese: 德天瀑布) are two waterfalls on the Quây Sơn River (Chinese: 桂春河), straddling the Sino-Vietnamese border, located in the Karst hills of Daxin County, Guangxi (Chinese side), and in Trùng Khánh District, Cao Bằng Province on the Vietnamese side, 272 km (169 mi) north of Hanoi.
In Vietnamese, the two falls are considered as two parts of one waterfall with the sole name Bản Giốc. The two parts are called as: thác chính (Main waterfall) and thác phụ (Subordinate waterfall). Chinese texts sometimes name both falls from the Détiān falls on the Chinese side. During the summer rains the two waterfalls may join together.