Map - Matsu Islands (Lienchiang)

The Matsu Islands ( or, ; Foochow Romanized: Mā-cū liĕk-dō̤), officially Lienchiang County (, ; Foochow Romanized: Lièng-gŏng-gâing), are an archipelago of 36 islands and islets in the East China Sea governed by the Republic of China (ROC) based in Taiwan, with its location sitting alongside southeastern coast of mainland China. It is the smallest county in the ROC-controlled territories by area and population, as well as one of two counties that were part of the nominal Fujian 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 which is now divided between the administrations of the ROC and the PRC.

Lienchiang County, Taiwan (R.O.C.) uses the traditional Chinese characters name (連江縣) and the romanized name Lienchiang which is derived from the Wade-Giles romanization (Lien²-chiang¹) of the Mandarin pronunciation for those Chinese characters that also refer to Lianjiang County, Fuzhou, Fujian in mainland China. Lienchiang has also been written as Lien-chiang and Lienkiang and by a postal romanization of the local language pronunciation Lienkong. The term Lienchiang can also refer to the homophonous Lianjiang in Zhanjiang, Guangdong, China.

The Matsu Islands are named after the main island, Nangan (Nankan). Nangan is also named Matsu Island because of a temple on the island which is supposed to be the burial site of the similarly named goddess Mazu (媽祖). Matsu is the Wade-Giles-derived romanization of the Mandarin pronunciation (Ma³-tsu³) for the Chinese character name (馬祖) of the islands. The Matsu Islands are also known by other Chinese-language names including and 馬祖島; Foochow Romanized: Mā-cū dō̤).

In April 2003, the Lienchiang County government considered changing the name of the county to Matsu County in order to avoid confusion with the nearby Lianjiang County on the mainland. Then-Magistrate Chen Hsueh-sheng said some local people opposed the name change because they felt it reflected the pro-independence viewpoint of the Democratic Progressive Party.