The Matsu Islands (UK: /ˌmætˈsuː/ or US: /ˌmɑːtˈsuː/) are an archipelago of 36 islands and islets in the East China Sea governed by the Republic of China (Taiwan), situated alongside the southeastern coast of mainland China. The archipelago forms Lienchiang County (/ljɛnˈdʒjɑːŋ/), the smallest county in the ROC-controlled territories by area and population, as well as one of two counties that is a part of the nominal Fuchien Province.
The current Lienchiang County of the ROC was once part of an intact Lienchiang County of Fujian before its effective partition in 1949 following the Chinese Civil War, which resulted in the mainland portion of the county being controlled by the People's Republic of China (PRC), while the offshore islands of Matsu remained under ROC control. The circumstance has made the county the only former geographical unit with the same name that is now divided between the administrations of the ROC and the PRC.