Chen Cheng in the context of "Tsotanhui Clique"

Martial law in Taiwan (Chinese: 戒嚴時期; pinyin: Jièyán Shíqí; Pe̍h-ōe-jī: Kài-giâm sî-kî) refers to the periods in the history of Taiwan after World War II, during control by the Republic of China Armed Forces of the Kuomintang-led regime. The term is specifically used to refer to the over 38-year-long consecutive martial law period between 20 May 1949 and 14 July 1987, which was qualified as "the longest imposition of martial law by a regime anywhere in the world" at that time (having since been surpassed by Brunei).

With the outbreak of Chinese Civil War, the "Declaration of Martial Law in Taiwan Province" (臺灣省戒嚴令; Táiwān Shěng Jièyán Lìng; Tâi-oân-séng Kài-giâm Lēng) was enacted by Chen Cheng, who served as the chairman of Taiwan Provincial Government and commander of Taiwan Garrison Command, on 19 May 1949. This order was effective within the territory of Taiwan Province (including Island of Taiwan and Penghu). The provincial martial law order was then superseded by an amendment of the "Declaration of Nationwide Martial Law", which was enacted by the central government after the amendment received a retroactive consent by the Legislative Yuan on 14 March 1950. Martial law in Taiwan Area (including Island of Taiwan, Penghu) was lifted by a Presidential order promulgated by President Chiang Ching-kuo on 15 July 1987.

As a result of the surrender and occupation of Japan at the end of World War II, the islands of Taiwan and Penghu were placed under the governance of the Republic of China (ROC), ruled by the Kuomintang (KMT), on 25 October 1945. Following the February 28 massacre in 1947, martial law was declared in 1949 by the Governor of Taiwan, Chen Cheng, and the ROC Ministry of National Defense. Following the end of the Chinese Civil War in 1949, the ROC government retreated from the mainland as the Chinese Communist Party (CCP) proclaimed the establishment of the People's Republic of China (PRC). The KMT retreated to Taiwan and declared Taipei the temporary capital of the ROC. For many years, the ROC and PRC each continued to claim in the diplomatic arena to be the sole legitimate government of "China". In 1971, the United Nations expelled the ROC and replaced it with the PRC.

In 1987, martial law was lifted and Taiwan began a democratisation process, beginning with the abolition of the Temporary Provisions and culminating with the first direct president election in 1996. By 2000, the Democratic Progressive Party (DPP) came to power and began to pursue Taiwanese independence and identity.