北部湾（越南语：Vịnh Bắc Bộ，英语：Beibu Gulf / Gulf of Tonkin），****沿用旧称东京湾，是位于南中国海西北部分沿陆封闭式海湾。

地理上东临琼、粤，北抵桂南，西到越南。总面积大约12.93万平方千米。

该地区是中国接触东南亚各国的海上交信道路，对中国的东南亚政策具有极其重要的意义。并且该地区海洋资源丰富，主要有鱼类、石油等资源，是中国的石油开采场地和主要渔场之一。在中国，于2008年成立了由广西南宁、北海、钦州和***所组成的广西北部湾经济区。

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.