Plaeng Yao (, ) is a district (amphoe) of Chachoengsao province, central Thailand.
The minor district (king amphoe) Plaeng Yao was established on 16 October 1978 with the three tambons: Plaeng Yao, Hua Samrong, and Wang Yen from Bang Khla district. It was upgraded to a full district on 15 March 1985.
Neighboring districts are (from the west clockwise): Ban Pho, Bang Khla, Ratchasan, Phanom Sarakham, and Sanam Chai Khet of Chachoengsao Province; and Ko Chan, Phanat Nikhom, and Phan Thong of Chonburi province.
Plaeng Yao is home to Toyota's Gateway Assembly Plant. It has been used to manufacture the Prius model.
Plaeng Yao district is divided into four sub-districts (tambons), which are further subdivided into 48 administrative villages (mubans).
There are four sub-district municipalities (thesaban tambons) in the district:
There are three sub-district administrative organizations (SAO) in the district: