Santi Suk (Thai: สันติสุข, pronounced [sǎn.tì(ʔ) sùk]; Northern Thai: สันติ๋สุ๋ข, [sǎn.tǐ(ʔ) sǔk]) is a district (amphoe) in the central part of Nan province, northern Thailand.

The minor district (king amphoe) Santi Suk was established on 15 June 1981, when the two tambons Du Phong and Pa Laeo Luang were split off from Mueang Nan district.

[4] Neighboring districts are, from the north clockwise, Tha Wang Pha, Pua, Bo Kluea, Mae Charim, Phu Phiang and Mueang Nan.

The eastern part of the district is in the Luang Prabang Range mountain area of the Thai highlands.

There are no municipal (thesaban) areas, and three tambon administrative organizations (TAO).