Citrus unshiu is a seedless and easy-peeling citrus species, probably of Japanese origin, introduced elsewhere. In Japan, it is known as mikan or formally unshu mikan (Japanese: 温州蜜柑, unshu mikan). In China, it is known as Wenzhou migan (Chinese: 温州蜜柑; pinyin: Wenzhōu Mėgan). The Japanese name is a result of the local reading of the same characters used in the Chinese. In both languages, the name meaning "Honey Citrus of Wenzhou", Wenzhou being a city in Zhejiang province, China. It is also often known as "Seedless mandarin".
Its fruit is sweet and usually seedless, about the size of other mandarin oranges (Citrus reticulata), smaller than an orange. One of the distinguishing features of the satsuma is the distinctive thin, leathery skin dotted with large and prominent oil glands, which is lightly attached around the fruit, enabling it to be peeled very easily in comparison to other citrus fruits. The satsuma also has particularly delicate flesh, which cannot withstand the effects of careless handling. The uniquely loose skin of the satsuma, however, means that any such bruising and damage to the fruit may not be immediately apparent upon the typical cursory visual inspection associated with assessing the quality of other fruits. In this regard, the satsuma is often categorised by citrus growers as a hit-and-miss citrus fruit, the loose skin particular to the fruit precluding the definitive measurement of its quality by sight and feel alone.
The Chinese and Japanese names reference Wenzhou, a city in the Zhejiang Province of China known for its citrus production. However, it has also been grown in Japan since ancient times, and the majority of cultivars grown in China today were cultivated in Japan and reverse-introduced into China in modern times. Clementines are not the same variety as the unshiu or mikan mandarin.
The satsuma originates from Japan. In 1916, a number of Japanese cultivars were introduced to Wenzhou. These, and new cultivars developed from them, now dominate orchards in Wenzhou. The traditional centre of satsuma production in Wenzhou is in the town of Wushan, in the Ouhai District of Wenzhou.