Ongkharak (Thai: องครักษ์, pronounced [ʔōŋ.kʰā.rák]) is a district (amphoe) in the western part of Nakhon Nayok province, central Thailand.

When he and his company arrived in the area of Ongkharak District, one of the royal guard fell ill and died.

Twenty years later, the office moved to a place next to the Saovabha Bhongsi Water Gate.

municipality (thesaban tambon) and covers parts of Ongkharak and Sai Mun subdistricts.

There are further eleven subdistricts administrative organizations - SAO (ongkan borihan suan tambon - o bo toh).