The Thurniaceae are a family of flowering plants composed of two genera with four species. The botanical name has been recognized by most taxonomists. The APG II system, of 2003, also recognizes such a family, and assigns it to the order Poales in the clade commelinids, in the monocots. The family consists of two genera, totalling only a few species, perennial plants of wet habitats in South America. This represents a slight change from the APG system, 1998, which treated the two genera as each constituting their own family (Prioniaceae and Thurniaceae), both placed in the order Poales.