Coordinates: 23°49′N 120°37′E / 23.817°N 120.617°E
Ershui Township (Chinese: 二水鄉; pinyin: Èrshuǐ Xiāng) is a rural township in southeastern Changhua County, Taiwan.
Ershui is bordered on the north by Tianzhong Township, to the east by Mingjian Township in Nantou County, and to the west by Xizhou Township. Its name means, literally, "Two Waters", which is a reference to the two irrigation canals constructed in the township, Babao canal 1 and 2, linking the waters from the nearby Zhuoshui River to the fertile Changhua Plain. Ershui is known for its picturesque scenery and the nearby Bagua Mountain Range, and offers many biking and hiking trails. The bulk of Ershui's population lives near its central plaza in front of the Ershui railway station, on the Western Line on the TRA's railway network.
Ershui encompasses 29.44 square kilometres (11.37 sq mi) and a population of 15,489, including 8,126 males and 7,363 females as of January 2017.
The township's former name (Chinese: 二八水; Pe̍h-ōe-jī: Jī-pat-chuí; literally: "two 'Pat' waters") refers to Babao canals 1 and 2, which take water from the Choshui River to irrigate the farmlands of Changhua. The canals are known as the "Mother Rivers of Changhua", spreading out in a fan-shaped distribution throughout Changhua county and creating a fertile plain for agriculture. During Japanese rule, the name was changed to Nisui Village (Japanese: 二水庄?), which was modified to Ershui Township after Taiwan's handover to the Republic of China in 1945.