One China

One China is a phrase with variant meanings, adopted by many states and other actors to describe their stance on the relationship between the People's Republic of China (PRC) based on mainland China, and the Republic of China (ROC) based on the Taiwan Area. "One China" asserts that there is only one de jure Chinese nation, despite the de facto division between the two rival governments in the aftermath of the Chinese Civil War. The term may refer, in alphabetical order, to one of the following:

After the Chinese Communist Party (CCP) defeated the Kuomintang (KMT) in the Chinese Civil War and the subsequent retreat of the ROC to Taiwan, the CCP established the PRC in mainland China while the ROC ruled over Taiwan and several outlying islands. During this time, both governments continued to claim legitimacy as the government of all of China. The KMT legally designated the Chinese Communist Party as a "rebellious group". Initially, international recognition of the two was split, but most countries began to recognize the PRC over the ROC in the 70s, including the United States in 1979. The language in the United States' One China policy first arose in its joint 1972 Communiqué with the PRC.

Under ROC President Lee Teng-hui in the 1990s, the Additional Articles of the Constitution of the Republic of China were passed which effectively transformed Taiwan from a one-party state into a democracy, and limited civil and political rights to citizens in the "free area" (the area under its de facto control, consisting of the island groups of Taiwan, Penghu, Kinmen, Matsu and some minor islands), but did not alter language regarding territorial claims or national territory.

Although the 1991 constitutional amendments localized governance to the "free area," the 1947 Constitution still claims all of China as ROC territory, aligning with the Kuomintang's (KMT) original "One China" stance. The Constitution defines ROC territory as encompassing all of China, based on its "existing national boundaries" at the time of adoption (Article 4), asserting the ROC as the legitimate government of the entirety of China, not solely Taiwan. This constitutional stance supports the KMT's historical vision, creating a legal-political disconnect under Democratic Progressive Party (DPP) governance. Despite the DPP's political dominance, it has not legally amended the Constitution to formally redefine Taiwan as a separate nation or change the national boundaries to exclude the mainland, not least because this could provoke PRC retaliation or even invasion. This deadlock reflects a split along party lines: Pan-Blue coalition parties (including the Kuomintang) adhere to "One China with respective interpretations", while Pan-Green coalition parties (including the Democratic Progressive Party) reject it. Meanwhile, the PRC has maintained its One China principle.

The Dutch established a colony on Taiwan in 1624 based in present-day Tainan. Shortly after, the Spanish established a colony in Northern Taiwan in 1626, but were driven out by the Dutch in 1642. It was during this time that large-scale Chinese migration from nearby Fujian Province began. The Dutch colony was later conquered by Zheng Chenggong (Koxinga), a Ming-loyalist, in 1662 as the Kingdom of Tungning, before being incorporated by the Qing dynasty in 1683 as part of Fujian Province. In 1887, it was officially made a separate Fujian-Taiwan Province. Taiwan remained a province for eight years until it was ceded to Japan under the Treaty of Shimonoseki in 1895 following the First Sino-Japanese War.

While Taiwan remained under Japanese control, the Qing dynasty was ousted and the First and Second Republic of China (ROC) were established from the Beiyang regime to the Kuomintang (KMT) from 1928. After the conclusion of World War II in 1945, the Republic of China was given control of Taiwan. In 1949, after losing control of most of mainland China following the Chinese Civil War, and before the post-war peace treaties had come into effect, the ROC government under the KMT withdrew to Taiwan, and Chiang Kai-shek declared martial law.

An argument has been made that Japan formally renounced all territorial rights to Taiwan in 1952 in the San Francisco Peace Treaty, but neither in that treaty nor in the peace treaty signed between Japan and China was the territorial sovereignty of Taiwan awarded to the Republic of China. The treaties left the status of Taiwan—as ruled by the ROC or PRC—deliberately vague, and the question of legitimate sovereignty over China is why China was not included in the San Francisco Peace Treaty. This argument is not accepted by those who view the sovereignty of Taiwan as having been legitimately returned to the Republic of China at the end of the war. Some argue that the ROC is a government in exile, while others maintain it is a rump state.

The ROC continued to claim itself as the rightful ruler of the entirety of China under the single-party KMT regime, and the PRC made a symmetric claim. In 1971, the United Nations General Assembly Resolution 2758 replaced the ROC's seat in the United Nations with the PRC. From 30 April 1991, the ROC officially recognized the PRC, thus abandoning the Hallstein Doctrine, while maintaining the claim of an exclusive mandate as the legitimate ruler of China. The ROC transformed into a free and democratic state in the 1990s following decades of martial law with the passage of the Additional Articles of the Constitution of the Republic of China. Afterwards, the legal and political status of Taiwan has become more contentious, with increasing public expressions in favor of Taiwan independence, which were formerly outlawed.