Kaeng Khoi is a district (amphoe) in the northeastern part of Saraburi Province, central Thailand.
The district was created in 1827 and called khwaeng Kaeng Khoi. The district office was in Ban Tan Diao. In 1897, the khwaeng was converted to an amphoe. The office of the district was moved from the Pa Sak River bank to the nearby Kaeng Khoi railway station in 1915. Its name Kaeng Khoi comes from Raeng Khoi that refers to 'vulture waiting'. Because the district in the past was the gateway to Dong Phaya Fai or Dong Phaya Yen (mountain range) today. The large rain forest is full of wildlife and malaria. Many people died while traveling here, so often the vultures gathered to wait to eat the corpses.
Neighboring districts are (from the north clockwise) Phatthana Nikhom of Lopburi Province, Wang Muang and Muak Lek of Saraburi Province, Mueang Nakhon Nayok and Ban Na of Nakhon Nayok Province, Wihan Daeng, Mueang Saraburi, and Chaloem Phra Kiat of Saraburi. The district marks the western end of Khao Yai National Park. In the southern part of the district is the Chet Khot-Pong Kon Sao Nature Study Centre, containing several waterfalls.
The district is divided into 14 sub-districts (tambons), which are further subdivided into 116 villages (mubans).