Xiyu Township (Chinese: 西嶼鄉; pinyin: Xīyǔ Xiāng; Wade–Giles: Hsi1-yü3 Hsiang1; Pe̍h-ōe-jī: Sai-sū-hiong; Pha̍k-fa-sṳ: Sî-yí-hiông) is a rural township encompassing Xiyu/Si Island/Hsi Island, also known as Fisher Island, Yuweng or Pescadores Island (漁翁島; Yúwēng Dǎo), which is among the three major islands of the Penghu County (the Pescadores), Taiwan. It has a population of 8,438 and an area of 18.7148 square kilometres. The major scenic spots include some forts and lighthouse. They were built or reconstructed in the Qing Dynasty, and were credited as of Taiwan.