Wu (吳), also called Wuyue (吳越), is a region in the Jiangnan area (the south of the Yangtze River), surrounding Suzhou, in the Jiangsu and Zhejiang provinces of China. The term "Wu" is also used as an abbreviation for several kingdoms based in the area. The two largest cities in the Wu region are Shanghai and Hangzhou. The Wu language and its dialects are spoken in this region.
The first Wu state was established in the late Western Zhou Dynasty. Once considered to be a vassal state of the Zhou Dynasty, it emerged as a major power among the various states in China at the end of the Spring and Autumn Period.
Go-on (呉音), which is one of the sources of Japanese pronunciation for kanji (the others being kan-on, tō-on and kan'yō-on), is sometimes said to have originated from this region. The Go- component in the name Go-on is cognate to the Chinese word Wu (Wu is the pronunciation for the Chinese character 吳 in Mandarin. However, in Wu language 呉 is usually pronounced as Ho, Oh, Ng, or Nguu).