Sian may refer to:
- Sian, a city in China (Also spelled Hsian or Xi'an)
- Siân, a Welsh girl's name
- Sian, or Seyan,سیان an Indian and Pakistani surname
- Sian, the original and common name for the Canadian band SIANspheric
- Stop the Islamisation of Norway, a Norwegian anti-Islamisation group which was established in 2008