Santo Tomás Mazaltepec is a town and municipality in Oaxaca in south-western Mexico.

The municipality covers an area of km².

It is part of the Etla District in the Valles Centrales region.

As of 2005, the municipality had a total population of 1,878, of whom 926 spoke an indigenous language (Zapotec).

This article about a location in the Mexican state of Oaxaca is a stub.