The South China Sea is a 3.5 million km² (1.4 million sq mi) marginal sea of the western Pacific, enclosed by southern China and Taiwan to the north, the Philippines to the east, Borneo and the Indonesian islands to the south, and Vietnam and the Malay Peninsula to the west. Its average depth is 1,212 m and its deepest point is about 5,560 m. Seven governments face its waters, and it holds hundreds of small islands, reefs and shoals, including the Paracel and Spratly Islands, Pratas and Scarborough Shoal, whose sovereignty is contested by several of those governments. About $3.4 trillion of the world's $16 trillion in seaborne trade crossed it in 2016, and the Spratly group alone contains more than 600 coral reefs.
From the Taiwan Strait to the Karimata Strait: Where the Sea Begins and Ends
The International Hydrographic Organization's Limits of Oceans and Seas (3rd edition, 1953) draws the northern edge of the sea on a line from the northern tip of Taiwan westward along the parallel of 25°24′N to the coast of Fujian. The eastern boundary follows Taiwan, the Luzon Strait islands, the west coast of Luzon, Mindoro and Palawan. The southern boundary crosses from the tip of the Malay Peninsula past Bintan and down the east coast of Sumatra to Bangka and Belitung, and then to the south-west corner of Borneo. A revised 1986 draft recognised a separate Natuna Sea, which would move the southern limit north to the Natuna Islands.
The sea connects to five neighbouring bodies of water: the East China Sea through the Taiwan Strait, the Philippine Sea through the Luzon Strait, the Sulu Sea through the channels around Palawan, the Java Sea through the Karimata and Bangka straits, and the Gulf of Thailand, which opens directly into it. The Gulf of Tonkin, between northern Vietnam and China's Hainan Island, is counted as part of the sea itself.
Rivers draining into it include the Pearl, Red, Mekong, Chao Phraya, Rajang, Kapuas, Musi, Pahang and Pasig.
A Drowned Shelf and a Basin 5,500 Metres Deep
Much of the sea floor is a drowned continental shelf. During the ice ages, when global sea level stood hundreds of metres lower, the Sunda Shelf in the south-west was dry land and Borneo was joined to mainland Asia. The deep basin in the centre has a different origin. It began to open around 45 million years ago when a block of crust known as the Dangerous Ground rifted away from southern China. Seafloor spreading followed from about 30 million years ago, propagating south-west to produce the V-shaped basin seen today, and stopped around 17 million years ago.
The central basin's deepest recorded point is either 5,559 m (18,238 ft) or 5,567 m (18,264 ft), depending on the survey. Sediment from the Mekong, Red and Pearl rivers has built deltas holding oil and gas.
The names differ around the rim. In China it is 南海 (Nán Hǎi, "South Sea"), and in Vietnam Biển Đông, the "East Sea". In September 2012 Philippine Administrative Order No. 29 directed government agencies to call the parts within the Philippine exclusive economic zone (EEZ) the West Philippine Sea, and in July 2017 Indonesia named the northern reaches of its own EEZ the North Natuna Sea.
Seven Coastlines: China, Taiwan, the Philippines, Malaysia, Brunei, Indonesia and Vietnam
Going clockwise from the north, the states and territories with coastlines on the sea are the People's Republic of China (PRC), the Republic of China (Taiwan), the Philippines, Malaysia, Brunei, Indonesia and Vietnam. Singapore sits at its south-western entrance, where the Singapore Strait leads to the Strait of Malacca, and Cambodia and Thailand front the Gulf of Thailand.
Some rim disputes have been settled by courts. In 2008 the International Court of Justice awarded Pedra Branca (Pulau Batu Puteh), at the eastern entrance of the Singapore Strait, to Singapore and the neighbouring Middle Rocks to Malaysia. In the Gulf of Thailand, where Malaysia, Cambodia, Thailand and Vietnam have overlapping claims, joint development areas share resources without settling sovereignty.
Paracels, Spratlys, Pratas and Scarborough Shoal: Who Claims and Who Holds What
The sea contains more than 250 small islands, atolls, cays, shoals, reefs and sandbars. They fall into five main groups: the Paracel Islands, the Spratly Islands, Pratas Island with the Vereker Banks, Macclesfield Bank and Scarborough Shoal. Both the PRC and Taiwan claim almost the whole sea within the "nine-dash line", a claim that overlaps with those of most other coastal states. The positions below are described, not endorsed.
- Paracel Islands. About 130 small coral islands and reefs spread over some 15,000 km² of sea. Claimed by the PRC, Taiwan and Vietnam. The PRC has controlled the whole group since the Battle of the Paracel Islands in January 1974, a clash in which 18 Chinese and 53 Vietnamese were killed. In July 2012 the PRC created the city of Sansha, in Hainan Province, to administer the area. Woody Island (213 ha) has more than 1,000 residents.
- Spratly Islands. Around 175 identified features spread across an area about 810 by 900 km, with only about 177 ha of naturally occurring land. Claimed in whole or in part by the PRC, Taiwan, Vietnam, the Philippines, Malaysia and Brunei. About 45 features are occupied, by Malaysia, the PRC, Taiwan, the Philippines and Vietnam; Brunei claims an EEZ that includes Louisa Reef but occupies no feature. Taiping Island (Itu Aba), the largest natural island at 46 ha, is administered by Taiwan. Thitu (Pag-asa), 37.2 ha, has been held by the Philippines since 1971. Malaysia has held Swallow Reef since 1983, and Vietnam administers Spratly Island. The PRC controls Fiery Cross Reef and Mischief Reef, where reclamation in the mid-2010s created an artificial island with a runway of about 2,700 m. At Second Thomas Shoal, Filipino marines have been stationed aboard BRP Sierra Madre since the Philippine Navy ran it aground there in 1999.
- Pratas Island. About 310 km south-east of Hong Kong, with an area of about 240 ha including a 64 ha lagoon, it is administered by Taiwan as part of Cijin District, Kaohsiung. The PRC claims it as part of Guangdong Province.
- Scarborough Shoal. A reef-ringed lagoon covering about 150 km², 220 km from Luzon. Its highest rock, South Rock, stands 1.8 m above high water. Claimed by the PRC, Taiwan and the Philippines. Since a 2012 standoff it has been under de facto PRC control, with the China Coast Guard regulating access to the lagoon; no permanent structures have been built there.
Shoals and banks are larger than they look on a map. Macclesfield Bank, a sunken atoll about 130 km long, covers 6,448 km² and is part of what China calls the Zhongsha Islands. Reed Bank in the north-east Spratlys, 8,866 km² and now 20 m below the surface, was an island until rising seas covered it about 7,000 years ago.
The 12 July 2016 Arbitral Award and the Responses to It
In January 2013 the Philippines started arbitration against the PRC under the UN Convention on the Law of the Sea (UNCLOS), covering the nine-dash line, the legal status of particular features and EEZ rights. The PRC did not take part. On 12 July 2016 the tribunal ruled for the Philippines on most of its submissions. It stated that it was not deciding sovereignty over any land territory and was not drawing any maritime boundary. It found that the PRC had no legal basis to claim historic rights to resources inside the nine-dash line beyond what UNCLOS provides. It classed Taiping Island and other Spratly features as "rocks", which are not entitled to a 200-nautical-mile EEZ, and it said that land reclamation and artificial-island building had caused severe harm to the coral reef environment.
The PRC rejected the award as "ill-founded" and continued to pursue bilateral talks with the Philippines. Taiwan, which administers Taiping Island, also rejected it. By November 2023, 26 governments had publicly supported the ruling, 17 had issued generally positive statements without calling for compliance, and eight had rejected it. The United Nations has taken no position on the merits.
$3.4 Trillion of Cargo and 10 Billion Barrels: The Sea Lanes
The sea links the Strait of Malacca with the ports of north-east Asia. Of the world's $16 trillion in seaborne trade in 2016, $3.4 trillion passed through it, and 2019 figures put its trade at the equivalent of about 5% of global GDP.
In 2023 about 10 billion barrels of crude oil and petroleum products and 6.7 trillion cubic feet of liquefied natural gas crossed the sea, the LNG alone amounting to 34% of world LNG trade. Under the sea floor, the US Energy Information Administration estimated in 2012–2013 that there were about 11 billion barrels of proved or probable oil and 190 trillion cubic feet of natural gas, most of it close to undisputed coastlines rather than near the Paracels or Spratlys.
Fishing Grounds of the Western Central Pacific
Catch statistics are reported for the wider Western Central Pacific fishing area, which includes most of the sea. In 2010 that area landed 11.7 million tonnes, about 14% of the world's commercial catch, up from under 4 million tonnes in 1970. At Scarborough Shoal, the 2016 arbitral award affirmed traditional fishing rights for both Filipino and Chinese artisanal fishers.
Reefs and Marine Life from the Spratlys to Dongsha Atoll
The Spratly group alone contains more than 600 coral reefs. Surveys there have recorded 2,927 marine species, including 382 species of hard coral, 524 species of marine fish, 262 species of algae and seagrass, 35 species of seabirds, and 20 species of marine mammals and sea turtles. In the north-east of the group, known as the Dangerous Ground, coral rises abruptly from depths greater than 1,000 m among low islands and sunken atolls, which makes the area hazardous to navigation.
Several reefs have been reshaped by reclamation. In April 2015 The New York Times reported Chinese dredgers turning Fiery Cross Reef and other reefs into military facilities. Other claimants have expanded features: Vietnam began reclamation at ten Spratly locations in 2016, more than doubling Spratly Island from its natural 15 ha to 36.5 ha by 2025, and Malaysia's work on Swallow Reef raised its dry land from 6.2 ha to 35 ha.
In the far north, Taiwan made Pratas Atoll the Dongsha Atoll National Park in January 2007, its first marine national park, protecting a circular reef with a shallow lagoon, shown in the photograph at the top of this page.
To see how the sea fits between Asia's other marginal waters, compare it with the shallower East China Sea beyond the Taiwan Strait, or look south-east to the Coral Triangle, which holds more than 76% of the world's shallow-water reef-building coral species.