Sarthe () is a French department in the northwest of the nation, named after the Sarthe River.
Na vzhodu meji na ozemlje Belfort, na jugu na Doubs in Juro, na zahodu na burgundski departma Côte-d'Or, na severozahodu na departma regije Šampanja-Ardeni Gornjo Marno, na severu pa meji na lorenske Vogeze.