Chiayi City (sometimes romanized as Jiayi) (Chinese: 嘉義市; Hanyu Pinyin: Jiāyì Shì; Tongyong Pinyin: Jiayì Shìh; Wade–Giles: Chia-i Shih; Pe̍h-ōe-jī: Ka-gī chhī) is a city located in the plains of southwestern Taiwan. Formerly called Kagee during the late Qing Dynasty and Kagi during the Japanese era, its historical name is Tirosen.

First inhabited by the Hoanya aborigines, the region was named Tirosen.

With the arrival of Han Chinese in southwestern Taiwan, the name Tirosen evolved to become Chu-lô-san (Chinese characters: 諸羅山) in Hokkien. Eventually, Chu-lô-san was shortened to simply Chu-lô. Because of the choice of the characters, it has been mistakenly suggested that the origin of the name Chu-lô-san or Chu-lô came from the expression "mountains surrounding the east." "Peach City" is another name for Chiayi City due to its peach-shaped territory in ancient times. The tip of the peach is around Central Fountain and was called "Peach-tip" by citizens.

Chulôsan was once the foothold to which people from the mainland immigrated. In 1621, Yen Szu-Chi, who came from Zhangzhou, Fujian Province, first led his people to cultivate this land after they landed at Penkang (Peikang). In 1661 (the 15th year of Yung-Li, Ming Dynasty), Koxinga defeated the Dutch based in Taiwan. Then he established one province, Cheng-Tien-Fu (承天府), and two counties, Tien-Hsing (天興縣) and Wan-Nien (萬年縣), demarcated by the Hsin-Kang River (新港溪, the Yen-Shui River now). Chiayi was under the jurisdiction of the Tien-Hsing County.