Santiago Nejapilla is a town and municipality located in the state of Oaxaca in southeastern Mexico. It is situated within the Teposcolula District, which lies in the center of the Mixteca Region.
The municipality is notable for its small population size, ranking as the fourth least populous municipality in the state of Oaxaca. It is more populous than only three other municipalities: Santiago Tepetlapa, Santo Domingo Tlatayapam, and Santa Magdalena Jicotlán.