Pai (Thai: ปาย, pronounced [pāːj]) is the northeasternmost district (amphoe) of Mae Hong Son province, northern Thailand.

Neighboring districts are (from west clockwise): Mueang Mae Hong Son, Pang Mapha of Mae Hong Son Province; Shan State of Myanmar; Wiang Haeng, Chiang Dao, Mae Taeng, Samoeng, and Galyani Vadhana of Chiang Mai province.

The district slogan is, "Pai River, worship Luang Pho Un Mueang, spread good kind of garlic, surrounded by lush forests, way of life evenly between hot and cold".

He ordered Prince Si Chai to attack Burmese army at Ban Don.

It is therefore very popular with both Thai and foreign tourists especially young people and also being used as a location for filming movies such as Ruk Jung in 2006, Pai in Love and Kat Rattakarn's Ya Kuet Nak-MV in 2009, Timeline in 2014 etc.