Mae Chai (Thai: แม่ใจ, pronounced [mɛ̂ː tɕāj]; Northern Thai: แม่ใจ๋, pronounced [mɛ̂ː tɕǎj]) is a district (amphoe) of the Phayao province in northern Thailand.

[1] It was recreated as a minor district (king amphoe) on 24 January 1963.

West of the town Mae Chai is the 1,426 m high Doi Luang mountain of the Phi Pan Nam Range.

It rises within a protected area in the Doi Luang National Park.

The district is divided into six sub-districts (tambons), which are further subdivided into 65 villages (mubans).