The Red River (Chinese: t 紅河, s 红河, p Hóng Hé; Vietnamese: Sông Hồng), also known as the Hồng Hà and Sông Cái (lit. "Mother River") in Vietnamese and the Yuan River (元江, Yuán Jiāng) in Chinese, is a river that flows from Yunnan in southwest China through northern Vietnam to the Gulf of Tonkin. According to C. Michael Hogan, the associated Red River Fault was instrumental in forming the entire South China Sea at least as early as 37 million years before present.