Sør-Audnedal (former spelling: Søndre Undal) is a former municipality that was located in the old Vest-Agder county in Norway.

On 1 January 1899, the western part of Sør-Audnedal (population: 1,734) was separated to become the new 63-square-kilometre (24 sq mi) municipality of Spangereid.

[3] The split left Sør-Audnedal with 2,958 inhabitants and an area of 171.7 square kilometres (66.3 sq mi).

On 3 November 1917, a royal resolution changed the spelling of the name of the municipality to Sør-Audnedal.

[9] The municipal council (Herredsstyre) of Sør-Audnedal was made up of representatives that were elected to four year terms.