Lahan Sai (Thai: ละหานทราย, pronounced [lā.hǎːn sāːj]) is a district (amphoe) in the southern part of Buriram province, northeastern Thailand.

The area was fertile and covered by dense forest, so people from neighboring districts moved to establish new village there.

When the community grew bigger, the government created a minor district (king amphoe) on 1 January 1961[1] to make it more comfortable for the citizen to reach public services.

[2] Lahan Sai means "plain fertile width hog deer" (Axis porcinus).

The non-municipal parts of Lahan Sai and the sub-districts Nong Takhrong and Khok Wan each have one tambon administrative organization (TAO).