Phayao is one of Thailand's seventy-seven provinces (changwat) lies in upper northern Thailand. Neighboring provinces are Nan, Phrae, Lampang, and Chiang Rai. In the northeast it borders Xaignabouli of Laos.

The provinces of Thailand are administrative divisions of the government of Thailand. The country is divided into 76 provinces proper, with one additional special administrative area. They are the primary local government units and act as juristic persons. They are divided into amphoe (districts) which are further divided into tambon, the next lower level of local government.