Don Sak (Thai: ดอนสัก, pronounced [dɔ̄ːn sàk]) is a district (amphoe) in eastern Surat Thani province.

The two principal ferry companies offering service to Samui Island leave from piers in the district.

Neighboring districts are (from the east clockwise): Khanom and Sichon, Nakhon Si Thammarat province); and Kanchanadit of Surat Thani.

[5] Don Sak District is divided into four sub-districts (tambons), which are further subdivided into 40 villages (mubans).

Travellers transiting from Surat Thani Airport en route to these islands typically embark from Don Sak.