Nine-dash line

The nine-dash line, also referred to as the eleven-dash line by Taiwan, is a set of line segments on various maps that accompanied the claims of the People's Republic of China (PRC, "mainland China") and the Republic of China (ROC, "Taiwan") in the South China Sea. The contested area includes the Paracel Islands, the Spratly Islands, the Pratas Island and the Vereker Banks, the Macclesfield Bank, and the Scarborough Shoal. Certain places have undergone land reclamation by the PRC, ROC, and Vietnam. The People's Daily of the PRC uses the term Duànxùxiàn (断续线) or Nánhǎi Duànxùxiàn (南海断续线; lit. 'South Sea intermittent line'), while the ROC government uses the term Shíyīduàn xiàn (十一段線; lit. 'eleven-segment line').

A 1946 map showing a U-shaped eleven-dash line was first published by the Republic of China government on 1 December 1947. In 1952, Mao Zedong of the PRC decided to remove two of the dashes in the Gulf of Tonkin amid warming ties with North Vietnam. However, the ROC government still uses the eleven-dash line. In 2013, some were surprised by a tenth dash to the east of Taiwan, but it had been present in PRC maps since as early as 1984. As of 2014, the PRC government had not clarified what it specifically claims in the map.

On 12 July 2016, an arbitral tribunal concluded that China's claim of historic rights over high seas has no lawful effect where they exceed the terms of the United Nations Convention on the Law of the Sea (UNCLOS). One of the arguments was that China had not exercised exclusive control over these waters and resources. The tribunal cannot rule on matters of territorial sovereignty, however. Over 20 governments have called for the ruling to be respected. It has been rejected by eight governments, including the PRC and the ROC.