Khao Saming (Thai: เขาสมิง, pronounced [kʰǎw sā.mǐŋ]) is a district (amphoe) in Trat province, eastern Thailand.

The district was established in 1898, but its name and the location of the district office had changed several times in its history. At first named Si Bua Thong, then Thung Yai, it was finally renamed Khao Saming when the district office was moved to Ban Tha Kathon in Tambon Khao Saming. The present district office building was opened on 14 February 2000.

Neighboring districts are (from the north clockwise) Khlung of Chanthaburi province, Bo Rai, Mueang Trat, Laem Ngop of Trat Province.

The district is divided into eight sub-districts (tambons), which are further subdivided into 66 villages (mubans). Two townships (thesaban tambon) are in the district: Saen Tung covers parts of the tambon Saen Tung, and Khao Saming covers parts of the tambon Khao Saming and Thung Nonsi. There are a further eight tambon administrative organizations (TAO).

1.	Khao Saming	เขาสมิง
2.	Saen Tung	แสนตุ้ง
3.	Wang Takhian	วังตะเคียน
4.	Tha Som	ท่าโสม
5.	Sato	สะตอ
6.	Pranit	ประณีต
7.	Thep Nimit	เทพนิมิต
8.	Thung Nonsi	ทุ่งนนทรี