The Gulf of Tonkin (Vietnamese:Vịnh Bắc Bộ, simplified Chinese:北部湾; traditional Chinese:北部灣; pinyin:Běibù Wān; Hainanese: Pak-pōe Oân) is a body of water located off the coast of northern Vietnam and southern China. It is a northern arm of the South China Sea. The Gulf is defined in the west by the northern coastline of Vietnam, in the north by China's Guangxi province, and to the east by China's Leizhou Peninsula and Hainan Island.