Đáy River

The Day River (Sông Đáy) is a river in Vietnam. It was formerly known as Hát River (Sông Hát or Hát Giang) or Gián Khẩu River (Sông Gián Khẩu). The river is a distributary of the Red River, draining into the Gulf of Tonkin.

The river has a length of 240 km and has a drainage basin of more than 7,500 km2, flowing through Hanoi, and the provinces of Hòa Bình, Hà Nam, Ninh Bình and Nam Định.