Lam Sonthi (Thai: ลำสนธิ, pronounced [lām sǒn.tʰíʔ]) is the easternmost district (amphoe) of Lopburi province, central Thailand.

The name Lam Sonthi comes from the small Sonthi River that originates in the Sap Langka Wildlife Sanctuary, the last forest of Lopburi, in Tambon Kut Ta Phet, in the very north of the district.

The district is divided into six sub-districts (tambons), which are further subdivided into 49 villages (mubans).

There are no municipal (thesaban) areas, and a further four tambon administrative organizations (TAO).

This Lopburi Province location article is a stub.