Xiyu Township is a rural township encompassing Xiyu/Hsiyu/Si Island/Hsi Island, also known as Fisher Island, Yuweng or Pescadores Island, which is among the three major islands of the Penghu County, Taiwan. It has a population of 8,301 and an area of 18.7148 square kilometres.

Townships are the third-level administrative subdivisions of counties of the Republic of China (Taiwan), along with county-administered cities. After World War II, the townships were established from the following conversions on the Japanese administrative divisions: