Mae Suai (Thai: แม่สรวย; IPA: [mɛ̂ː sǔaj]) is a district (amphoe) in the western part of Chiang Rai Province, northern Thailand.
Neighboring districts are (from the northeast clockwise) Mueang Chiang Rai, Mae Lao, Phan, Wiang Pa Pao, Phrao, Chai Prakan, Fang, Mae Ai of Chiang Mai Province.
The Khun Tan Range stretches from north to south along the western side of the district. The Suai River, a tributary of the Lao River, gives its name to the district.
The district was created in 1905, when the districts Mueang Wiang Pa Pao and Mueang Phong were merged. Originally spelled แม่ซ่วย, the current spelling was adopted before 1917.
The district is subdivided into 7 subdistricts (tambon), which are further subdivided into 128 villages (muban). Mae Suai and Chedi Luang are two subdistrict municipalities (thesaban tambon) which each cover part of the same-named tambon. There are further 9 Tambon administrative organizations (TAO).