Wiang Sa (Thai: เวียงสระ, pronounced [wīa̯ŋ sàʔ]) is a district (amphoe) of Surat Thani province, Thailand.

Neighboring districts are (from the west clockwise) Phrasaeng, Khian Sa, and Ban Na San of Surat Thani, and Phipun, Chawang, and Tham Phannara of Nakhon Si Thammarat province.

To the west the terrain descends to the Tapi plain, to the east are the hills of the Nakhon Si Thammarat mountain range.

Wiang Sa originated as a minor city-state (mueang) under the control of Nakhon Si Thammarat after the Srivijaya times.

It was converted into a district named Khlong Tan (คลองตาล) during the thetsaban reforms at the end of the 19th century.