Phayao (Thai พะเยา) is ane o the northren provinces (changwat) o Thailand. Neighborin provinces are (frae east clockwise) Nan, Phrae, Lampang an Chiang Rai. In the north-east it borders Xaignabouli o Laos.
The ceety o Phayao is locatit at the Phayao lake (Kwan Phayao) in the valley o the Ing River. Three big muntains surroond the valley, the Doi Luang (1697m), Doi Khun Mae Fat (1550m) an Doi Khun Mae Tam (1330m).
After Phayao wis foondit in 1096 it wis a sma ceety-state kinrick. In the 13t century it gained enough importance tae be equal partner o Keeng Mengrai o Lannathai an the Sukhothai Kinrick. Housomeivver a later keeng o Lannathai captured Phayao in 1338, and made it pairt o Lannathai. Durin the Burmese rulership o Lannathai the ceety became desertit, an in 1897 became pairt o the province Chiang Rai. Becomin effective on August 28, 1977 it wis split aff frae Chiang Rai again, an became a province o its awn.