Si Mahosot (Thai: ศรีมโหสถ, pronounced [sǐː mā.hǒː.sòt]) is a district (amphoe) of Prachinburi province, eastern Thailand.

Neighboring districts are (from the west clockwise): Ban Sang, Mueang Prachinburi and Si Maha Phot of Prachinburi Province; and Phanom Sarakham of Chachoengsao province.

The minor district (king amphoe) Khok Pip was established on 15 February 1970, when the three tambons, Khok Pip, Khu Lam Phan, and Phai Cha Lueat were split off from Si Maha Phot district.

[1] It was upgraded to a full district on 13 April 1977,[2] and renamed Si Mahosot on 3 June 1993.

[3] The district is divided into four sub-districts (tambons), which are further subdivided into 24 villages (mubans).