Fluminimaggiore is a comune (municipality) in the Province of Carbonia-Iglesias in the Italian region Sardinia, located about 60 km northwest of Cagliari and about 30 km north of Carbonia. As of 31 December 2004, it had a population of 3,065. The town has an area of 108.1 km².
Fluminimaggiore borders the following municipalities: Arbus, Buggerru, Domusnovas, Gonnosfanadiga, Iglesias.
There are several museums in the town, including a paleontology museum.