Sam Chai (, ) is a district (amphoe) in the northern part of Kalasin province, northeastern Thailand.
Neighboring districts are (from the east clockwise): Kham Muang, Sahatsakhan, and Nong Kung Si of Kalasin Province and Wang Sam Mo of Udon Thani province.
The minor district (king amphoe) was created on 1 April 1995, when it was split off from Kham Muang district.
On 15 May 2007, all 81 minor districts were upgraded to full districts. With publication in the Royal Gazette on 24 August, the upgrade became official.
The district is divided into four sub-districts (tambons), which are further subdivided into 46 villages (mubans). There are no municipal (thesaban) areas, and four tambon administrative organizations (TAO).