The South China Sea is a massive body of water in Southeast Asia, bordered by China, Taiwan, Vietnam, the Philippines, Malaysia, Brunei, and Indonesia. Roughly 3.5 million square kilometers in total area, it sits at the crossroads of some of the world’s busiest shipping lanes and contains rich fishing grounds, significant oil and gas reserves, and hundreds of disputed islands and reefs. It is one of the most strategically important and politically contested bodies of water on Earth.
Where the South China Sea Is
The sea stretches from the Strait of Malacca and Singapore in the southwest to the Strait of Taiwan in the northeast. Its deep-sea basin alone covers about 551,000 square kilometers, roughly 16% of the total area. Two major island chains sit within it: the Paracel Islands in the north and the Spratly Islands farther south. Both are small, many little more than rocks or coral reefs, but their location gives them outsized importance for controlling shipping routes, monitoring military activity, and claiming the waters around them.
The sea connects the Indian Ocean to the Pacific, making it one of the world’s most critical maritime corridors. The Strait of Malacca, which feeds directly into the South China Sea, is the largest oil transit chokepoint on the planet. In 2023, an estimated 23.7 million barrels of oil per day passed through it, including 16.6 million barrels of crude oil and condensate and 7 million barrels of petroleum products.
Why It Matters for Global Trade
More than 30% of the world’s maritime crude oil trade moves through the South China Sea. In 2016, that amounted to roughly 15 million barrels per day. Beyond oil, container ships carrying electronics, manufactured goods, and raw materials between East Asia, Europe, and the Middle East transit these waters daily. Any disruption here would ripple through global supply chains almost immediately.
Singapore, sitting at the sea’s southwestern entrance, serves as a major refining and transit hub. For energy-importing nations like China, Japan, and South Korea, the South China Sea is the primary route for fuel shipments. That dependence makes freedom of navigation through these waters a core concern for governments and militaries across the region and beyond.
Fishing and Food Security
The South China Sea accounted for 12% of global fish catch in 2015, and more than half the world’s fishing vessels are estimated to operate there. Its fisheries officially employ around 3.7 million people, though the real number is likely much higher when unregistered and small-scale operations are counted. For coastal communities in Vietnam, the Philippines, and southern China, these waters are a primary source of both protein and income.
Overfishing is a growing problem. Competition among nations has intensified as fish stocks decline, and large industrial fleets increasingly operate in waters that smaller, traditional fishing boats have relied on for generations. Fishing disputes often serve as a proxy for the broader territorial conflicts in the region.
Who Claims What
The South China Sea’s territorial disputes are among the most complex in the world, involving seven governments with overlapping claims. At the center is China’s sweeping claim, historically marked by a dashed line on maps (originally nine dashes, now sometimes drawn as ten). This line, first published in 1947 by the Nationalist government of the Republic of China, encloses the vast majority of the sea. The People’s Republic of China continued using these maps after 1949 and has since asserted “indisputable sovereignty” over the islands within the line and the adjacent waters, seabed, and subsoil.
China, Taiwan, and Vietnam all claim the Paracel Islands. The Spratly Islands are even more contested: China, Taiwan, and Vietnam each claim all of them, while Brunei, Malaysia, and the Philippines claim portions. The Philippines also claims Scarborough Shoal, a reef closer to its coast that China and Taiwan likewise claim. Brunei asserts a 200-nautical-mile exclusive economic zone that overlaps with China’s dashed line. Indonesia agreed with Vietnam on maritime boundaries in the South China Sea at the end of 2022 but has objected to China’s expansive claims.
Each country bases its position on a different mix of historical presence, geographic proximity, and international maritime law. China’s 1992 territorial sea law claims a 12-nautical-mile territorial sea around the Paracel Islands, Spratly Islands, Pratas Islands, and other features. Its 1998 law establishes a 200-nautical-mile exclusive economic zone and continental shelf rights. Vietnam, the Philippines, Malaysia, Indonesia, and Brunei all have maritime zones extending from their mainland coasts into the same waters.
The 2016 Arbitration Ruling
In 2013, the Philippines brought a case against China before an international tribunal at the Permanent Court of Arbitration in The Hague. The case challenged China’s historic rights claims, questioned the legal status of specific reefs and rocks, and accused China of violating international maritime law. China refused to participate in the proceedings.
The tribunal issued its final ruling on July 12, 2016, largely siding with the Philippines. It found that China’s claims to historic rights over the resources within the dashed line had no legal basis under the United Nations Convention on the Law of the Sea. The ruling also classified several features China had built on as rocks or low-tide elevations rather than islands, meaning they could not generate the large exclusive economic zones China claimed. China rejected the ruling and has not complied with it, calling it “null and void.” The decision remains a major point of tension in the region.
Artificial Islands and Military Buildup
Between December 2013 and October 2015, China constructed artificial islands totaling close to 3,000 acres on seven coral reefs it occupies in the Spratly Islands. These features were built by dredging sand from the seafloor and piling it onto existing reefs, then topping the new land with runways, radar installations, and port facilities. Several now host advanced air defense systems capable of early threat detection and monitoring of surrounding waterways.
The construction destroyed or severely damaged the coral reefs underneath, ecosystems that had supported marine biodiversity and fish populations for the surrounding region. The Paracel and Spratly Islands have become focal points for military competition among the bordering nations, with Vietnam, the Philippines, Malaysia, and Taiwan also maintaining smaller outposts on various features. The scale of China’s buildup, however, far exceeds that of any other claimant.
Oil and Gas Reserves
The seabed beneath the South China Sea holds significant oil and natural gas deposits, though estimates of their size vary widely and much of the area remains underexplored. The contested nature of the waters makes surveying and drilling politically fraught. Several bordering countries have developed oil and gas fields in less disputed areas closer to their own coasts, particularly Vietnam, Malaysia, and Brunei, but the potentially larger reserves in deeper, more contested waters remain largely untapped.
Control over these energy resources is one of the driving forces behind the territorial disputes. For China, which imports a large share of its energy, securing access to South China Sea reserves is a strategic priority. For smaller claimants like Brunei and Malaysia, offshore oil and gas production is a significant part of their national economies, making the boundaries drawn in these waters a matter of direct economic survival.