Si Chiang Mai (, ) is a district (amphoe) in the western part of Nong Khai province, northeastern Thailand. It may also be spelled Sri Chiang Mai.
Si Chiang Mai district was established by King Setthathirath of Lan Xang Kingdom. It was named after Chiang Mai, the hometown of his grandmother, the former queen of Chiang Mai (his mother was the princess from Lan Na). It was created as a district of Nong Khai Province on 4 August 1958, when it was split off from Tha Bo district.
Si Chiang Mai is bordered by the following districts of Nong Khai Province: Tha Bo, Pho Tak, and Sangkhom of Nong Khai Province. To the north across the Mekong River is the Lao province Vientiane Prefecture. A basalt plateau is flanked by the Mekong River to the north.
Si Chiang Mai is divided into four sub-districts (tambons), which are further subdivided into 43 administrative villages (mubans).
<small>The missing number is a tambon which now forms Pho Tak District.</small>
There are two sub-district municipalities (thesaban tambons) in the district:
There are three sub-district administrative organizations (SAO) in the district: