Pho Sai (Thai: โพธิ์ไทร, pronounced [pʰōː sāj]) is a district (amphoe) in the northeastern part of Ubon Ratchathani province, northeastern Thailand.

[2] Pho and sai trees are kinds of Ficus species that grow in Wat Si Bunrueang.

Neighboring districts are (from the southeast clockwise) Si Mueang Mai, Trakan Phuet Phon, Kut Khaopun, Khemarat, and Na Tan.

The district is divided into six sub-districts (tambons), which are further subdivided into 68 villages (mubans).

There are a further six tambon administrative organizations (TAO), all part of Ubon Ratchathani Province.