- Siyi or Si Yi 四邑, ("Four Counties"), is a region in southern Guangdong province
Siyi may also refer to:
- Siyi dialect 四邑方言, a branch of Yue Chinese spoken in Sze Yup
- Siyi (Four Barbarians) 四夷, a historical term for all non-Chinese peoples
- Four Arts or Siyi 四藝, artistic accomplishments for a Chinese scholar-bureaucrat
Siyi (sometimes spelled Sze Yup and variants) refers to the four former counties of Xinhui, Taishan, Kaiping and Enping in the Pearl River Delta of southern Guangdong province, China.
Siyi was a derogatory Chinese name for various peoples bordering ancient China, namely, the Dongyi 東夷 "Eastern Barbarians", Nanman 南蠻 "Southern Barbarians", Xirong 西戎 "Western Barbarians", and Beidi 北狄 "Northern Barbarians".