Sør-Odal is a municipality in Hedmark county, Norway. It is part of the traditional region of Odalen. The administrative centre of the municipality is the village of Skarnes.

The parish of Søndre Odalen was established as a municipality on 1 January 1838 (see formannskapsdistrikt).

The municipality is a rural community situated along the river Glåma and around the southern side of the lake Storsjøen. It is bordered by the municipalities of Eidskog in the south, by Kongsvinger in the east, and by Nord-Odal and Grue in the north. The terrain is dominated by rolling hills, lakes, and pine forests.

The last element is the old district name Odal (Old Norse: Ódalr). The first element of this is ó, a sideform of á which means "river" (here the Glåma river). The last element is dalr which means "valley" or "dale".

The first element Sør- (meaning "southern") was added after 1819 when the parish of Odal was divided in two. (See Nord-Odal.)

The coat-of-arms is from modern times. They were granted on 10 January 1992. The arms show three gold keys on a red background. They represent the three parishes of Oppstad, Strøm, and Ulleren and the three local bodies of water: Glomma, Oppstadåa, and Storsjøen. The key symbolizes justice, knowledge, and positive ideals. The arms were designed by Harald Hallstensen.