Tonstad is the administrative centre of the municipality of Sirdal in Agder county, Norway.

The village is located at the northern end of the lake Sirdalsvatnet in the Sirdalen valley.

The 1.14-square-kilometre (280-acre) village has a population (2015) of 874, giving the village a population density of 767 inhabitants per square kilometre (1,990/sq mi).

In 1960, it became the part of Sirdal, and it continued to be the administrative center of that new municipality.

The first element of the name comes from the female name Tone (Old Norse: Þorný) and the last element is staðir which means "homestead" or "farm".