It is located in the Satakuntaregion. The municipality had a population of 3,408 (2003) and covered an area of 149.88 km2 of which 0.22 km2 is water. The population density was 22.7 inhabitants per km2.
In Kiukainen there are many ancient gravehills made from piled stones. Largest of them is called Kuninkaanhauta, "the king's grave", located in the Panelia village. It is the biggest of its type in Nordic countries. The Stone Age Kiukainen culture is named after Kiukainen municipality.