Sør-Aurdal is a municipality in Oppland county, Norway. It is part of the traditional region of Valdres. The administrative centre of the municipality is the village of Bagn.

The parish of Søndre Aurdal was established as a municipality on 1 January 1838 (see formannskapsdistrikt). The area of Bruflat was transferred from Sør-Aurdal to Etnedal on 1 January 1894.

The Old Norse form of the name was Aurardalr. The first element is the genitive case of the old river name Aur (now called Bøaelva) and the last element is dalr which means "valley" or "dale". The old river name is derived from aurr meaning "gravel". The name Sør-Aurdal means '(the) southern (part of) Aurdal'. (The parish of Aurdal was divided in 1805.)

The coat-of-arms is from modern times. They were granted by royal decree on 9 February 1990. It is blue with gold silhouette of the gilt-copper medieval reliquary (chasse) that is still found in the Hedal stave church, but with five blue arches inspired by the arches on a similar medieval chasse from the medieval St. Thomas Church at Filefjell and representing the five Lutheran parishes of the municipality. It was chosen because Sør-Aurdal is one of two municipalities in Norway that have two stave churches that are still in use. The color blue was chosen to represent the two river systems in the municipality that were historically important for the logging industry and sawmills in Sør-Aurdal.

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