The Day River (Vietnamese: 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.
| Đáy River | |
|---|---|
 Day River through Ninh Phúc Port | |
| Location | |
| Country | Vietnam |
| Region | Hà Nội, Hòa Bình, Hà Nam, Ninh Bình and Nam Định |
| Physical characteristics | |
| Source | |
| • location | Geladaindong Peak, Tanggula Mountains, Qinghai (Đan Phượng) |
| • elevation | 5,042 m (16,542 ft) |
| Mouth | |
• location | Kim Sơn |
• coordinates | 19°54′47″N 106°05′42″E / 19.91306°N 106.09500°E |
• elevation | 0 m (0 ft) |
| Length | 240 km (150 mi) |
The river has a length of 240 km[1] and has a drainage basin of more than 7,500 km2,[2] flowing through Hanoi, and the provinces of Hòa Bình, Hà Nam, Ninh Bình and Nam Định.