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.

Taiwan, officially the Republic of China (ROC), is a country in East Asia. It is located at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northeast, and the Philippines to the south. The territories controlled by the ROC consist of 168 islands with a combined area of 36,193 square kilometres. The main island of Taiwan, also known as Formosa, has an area of 35,808 square kilometres, with mountain ranges dominating the eastern two-thirds and plains in the western third, where its highly urbanized population is concentrated. The capital, Taipei, forms along with New Taipei City and Keelung the largest metropolitan area. With around 23.9 million inhabitants, Taiwan is among the most densely populated countries.