São Martinho da Serra is a municipality in the state of Rio Grande do Sul, in southern Brazil. It is one of the many municipalities that make up this state, which is Brazil's southernmost and shares borders with Argentina and Uruguay.
As a municipality, São Martinho da Serra forms part of the local administrative structure of Rio Grande do Sul, with its own municipal government responsible for local services and governance. The state of Rio Grande do Sul is divided into hundreds of such municipalities, each varying widely in size and population.
Detailed information about the town's history, population, economy, and geography is limited in available sources. It should not be confused with other places bearing the name São Martinho elsewhere in Brazil or Portugal.