The Republic of China (ROC), or simply China, was a sovereign state based on mainland China from 1912 to 1949 prior to the government's relocation to Taiwan, where it continues to be based today. The ROC was established on 1 January 1912 during the Xinhai Revolution against the Qing dynasty, ending the imperial history of China. The Republican government was ruled by the Kuomintang (KMT) as a one-party state based in Nanjing from 1927, until its flight to Taipei on 7 December 1949 following the KMT's de facto defeat by the Chinese Communist Party (CCP) in the Chinese Civil War. The CCP proclaimed the People's Republic of China on 1 October 1949, while the ROC retains control over the "Free Area", with the political status of Taiwan remaining in dispute to this day.

The retreat of the government of Republic of China to Taiwan, also known as the Kuomintang's retreat to Taiwan or the Great Retreat in Taiwan, refers to the exodus of the remnants of the then-internationally-recognized Kuomintang-ruled government of the Republic of China (ROC) to the island of Taiwan (Formosa) on December 7, 1949, after losing the Chinese Civil War in the Chinese mainland. The Kuomintang, its officers, and approximately 2 million ROC troops took part in the retreat, in addition to many civilians and refugees, fleeing the advance of the People's Liberation Army of the Chinese Communist Party (CCP). The CCP, who now effectively controlled most of Mainland China, spent the subsequent years purging any remnant Nationalist agents and bandits in western and southern China, solidifying the rule of the newly established People's Republic of China.