Schoenoplectus americanus (syn. Scirpus americanus) is a species of flowering plant in the sedge family known by the common names chairmaker's bulrush and Olney's three-square bulrush. It is native to the Americas, where it is known from Alaska to Nova Scotia and all the way into southern South America; it is most common along the East and Gulf Coasts of the United States and in parts of the western states. It grows in many types of coastal and inland wetland habitat, as well as sagebrush, desert scrub, chaparral, and plains. This rhizomatous perennial herb easily exceeds two meters in height. The stiff stems are sharply three-angled and usually very concave between the edges. Each plant has three or fewer leaves which are short and narrow. The inflorescence is a small head of several spikelets which may be brown to bright orange, red, purplish, or pale and translucent. They have hairy edges. The fruit is a brown achene. The plant reproduces sexually by seed and colonies spread via vegetative reproduction, sprouting from the rhizomes.
(Pers.) Volkart ex Schinz & R. Keller
Native American groups used this plant for many purposes, including food, basketry, and hatmaking. It is used for revegetation projects in salt marsh habitat in its native range. It is a model organism in the study of salt marsh ecology and its response to climate change (currently global warming).