Sikhiu (Thai: สีคิ้ว, pronounced [sǐː.kʰíw]) is a district (amphoe) in the western part of Nakhon Ratchasima province, Thailand.

Originally known as Mueang Nakhon Chantuek, Sikhio is an ancient frontier city between the Thai-dominated Chao Phraya valley and the Lao-dominated Khorat Plateau.

Nakhon Chantuek was controlled directly by the central government of Siam.

There is evidence as paintings on the cave walls on local hill, Khao Chan Ngam.

Neighbouring districts are (from the north clockwise): Dan Khun Thot, Sung Noen, and Pak Chong of Nakhon Ratchasima; Muak Lek of Saraburi province; and Lam Sonthi of Lopburi province.