The Taiwan Strait or Formosa Strait, also known as the Black Ditch (Chinese: 烏水溝; Pe̍h-ōe-jī: O͘-chúi-kau), is a 180 kilometres (110 mi) wide strait separating the island of Taiwan from the Asian mainland. The strait is part of the South China Sea and connects to the East China Sea to the north. The narrowest part is 130 km (81 mi) wide.
Fujian Province in China is to the west of the strait while the islands of Kinmen, Xiamen, Pingtan and Matsu lie just off the coast. To the east of the Strait are the west coasts of Taiwan and Penghu. The island fishermen use the strait as a fishing resource. The Min and Jiulong rivers empty into the strait. Taiwan also administers Penghu, Kinmen, and Matsu.
The Strait has been the theatre for several military confrontations between China and Taiwan since the last days of the Chinese Civil War in 1949 when the Kuomintang (KMT) forces led by Generalissimo Chiang Kai-shek retreated across the Strait and relocated their government to their final stronghold of Taiwan. A theoretical median maritime border known as the cross-strait median (海峽中線) also exists on the water to prevent certain transportation from passing.
As part of the People's Republic of China's National Expressway Plan, a tunnel or possibly a bridge, was proposed in 2005 to link the city of Fuzhou with Taipei across the strait. If such an extreme construction would ever be built, it would by far exceed the length of any man-made tunnel in the world today. Engineers in Beijing state that a tunnel is technically feasible. However, the Republic of China government has refused to open direct links out of concern for Taiwan's security and in fear that by doing so it would have to recognize the People's Republic of China's one-China policy.