the pipewort order of monocotyledonous flowering plants (i.e., those characterized by one seed leaf), consisting of one family, Eriocaulaceae, with 13 genera of small, tufted herbs with grasslike leaves that grow in aquatic and marshy habitats, mostly in tropical and subtropical regions, especially in South America.

The plants are characterized by inconspicuous flowers that are borne in small but often showy clusters, resembling superficially those of a sunflower. The flowers are either male or female, but the heads may contain flowers of only one sex or of both sexes together.

The order is considered to have a common evolutionary origin with the spiderwort order (Commelinales) from an ancestor in the lily order (Liliales). The chief genera are Paepalanthus (485 species), Eriocaulon (400 species), Syngonanthus (195 species), and Leiothrix (65 species). About 30 species of Eriocaulon occur outside the tropics in Japan, about 8 occur in eastern North America, and only 1 (E. septangulare) is known in Europe.