The Spratlys Archipelago in the South China Sea (called by Vietnam the East Sea) is disputed in various degrees by China; Taiwan; Vietnam; Philippines; Malaysia and Brunei. The Paracels Islands are disputed between China and Vietnam; but have been controlled completely by China since 1974.

The Chinese claim is the most extensive and is generally indicated by a notional frontier termed by the Chinese the 'Nine Dotted Line' (n醤hai jiudu鄋 xi鄋; literally "Nine division lines of the South China Sea") and by the Vietnamese the 'Ox's Tongue Line' (衭?ng lu?i b?.

The Nine-dotted line was originally an 'eleven dotted line' first indicated by the then Kuomintang government of the Republic of China in 1947 for its claims to the South China Sea. After the Communist Party of China took over mainland China and formed the People's Republic of China in 1949; the line was adopted and revised to nine as endorsed by Zhou Enlai. The 9-dotted line is subject to severe criticism and protest from many countries in the region. Immediately after China submitted to the UN a map including the 9-dotted lines territorial claim in the South China Sea on May 7; 2009; the Philippines lodged a diplomatic protest against China for claiming the whole of South China Sea illegally. Vietnam and Malaysia filed their joint protest a day after China submitted its 9-dash line map to the UN.