Go-on (, Japanese pronunciation: [?o.o?][note 1], "sound from the Wu region") are one of the several possible ways of reading Japanese kanji. They are based on the classical pronunciations of Chinese characters of the then-prestigious eastern Jiankang (now Nanjing) dialect.
Introduced to Japan during the 5th and 6th centuries, when China was divided into separate Northern and Southern dynasties, go-on readings are possibly imported either directly from the Southern dynasty or the Korean Peninsula. This explanation is based mainly on historical reasoning: there was an influx of thinkers from China and Korea to Japan at that time, including both Buddhist and Confucian practitioners. However, there is no historical documentation to conclusively demonstrate that go-on readings are actually based on southern Chinese.
That being said, Shibatani has noted that go-on readings make up the first of three waves of Chinese loans to the Japanese language, the others being kan-on and tou-sou-on (meaning Tang Song sound), with go-on mainly associated with Buddhism 
Go-on readings are particularly common for Buddhist and legal terminology, especially those of the Nara and Heian periods. These readings were also used for the Chinese characters of the ancient Japanese syllabary used in the Kojiki.
When kan-on readings were introduced to Japan, their go-on equivalents did not disappear entirely. Even today, go-on and kan-on readings still both exist. Many characters have both pronunciations. For instance, the name Sh?toku (in go-on) is pronounced as such in some derived place-names, but Seitoku (in kan-on) in others. Both are possible today, depending on what is being referred to.
However, some go-on sounds are now lost. Even though monolingual Japanese dictionaries list a complete inventory of go-on for all characters, some were actually reconstructed using the fanqie method or were inferred to be the same as their modern homophones.
Go-on readings were formerly referred to as Wa-on (, lit. "Japanese sound"). The term 'go-on' was first introduced in the mid-Heian, likely by people who wished to promote kan-on readings. During the Tang dynasty, people in Chang'an referred to their own way of reading characters as qíny?n (, shin'on, lit. "Qin sound") and all other readings, particularly those originating south of the Yangtze, as wúy?n (, go'on, lit. "Wu sound") or one of many other similar names. It is thought that Japanese students studying in China adopted this practice, and, taking the position that the Chang'an-based manner of elocution were the correct ones, they also began to refer to the previously imported, unfashionable kanji readings as "go-on".
Go-on readings were also occasionally referred to as Tsushima-on () and Kudara-on (, literally "Baekje sound") because of a story that claims a Baekjean nun named H?mei () had taught Buddhism in Tsushima by reading the Vimalak?rti Sutra entirely in go-on. Because of this, go-on has been dubbed "imitations of Korean imitations."
Go-on readings are generally less orderly than kan-on readings, but can be characterized as follows.
|character/word||Go-on ()||Kan-on ()|
Most of the content of this article comes from the equivalent Japanese-language article, accessed on June 5, 2006.