Bo Hai (渤海 pinyin bó hăi, lit. "Bo Sea"), also known as (though redundant) Bohai Sea or Bohai Gulf, is the innermost gulf of the Yellow Sea on the coast of northeastern China. It is approximately 823,000 km². In literature before early 20th century, Bo Hai was, officially until January 1929, sometimes called "Gulf of Chih-li", where "Chih-li" (contemporary Wade-Giles for Zhili) was an old name for Hebei Province.
The gulf is formed by the Liaodong Peninsula to the northeast and the Shandong Peninsula to the south. Bo Hai consists of three bays: Laizhou Bay to the south, Liaodong Bay to the north, and Bohai Bay to the west. The rivers Huang He, Liao He, and Hai He empty into Bo Hai.
Bo Hai borders Shandong province, Liaoning province, Hebei province, and Tianjin municipality. Port cities on Bo Hai coast include Dalian, Yingkou, Jinzhou, Qinhuangdao, Tanggu, Longkou and Yantai.
In recent decades, petroleum and natural gas deposits were discovered in and around Bo Hai.
Islands include: