The Loir is a 319 km (198 mi) long river in western France. It is a left tributary of the Sarthe. Its source is in the Eure-et-Loir department, north of Illiers-Combray. It joins the river Sarthe in Briollay, north of the city of Angers.

It is indirectly a tributary of the Loire, and runs roughly parallel to it and slightly north of it for much of its length, and so might be regarded as a Yazoo type river.^{[citation needed]}