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

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).