Isolepis cernua (basionym Scirpus cernuus) is a species of flowering plant in the sedge family known by the common names low bulrush, slender club-rush, tufted clubrush, and fiberoptic grass. It is widespread, being native to many regions of the world, including parts of Australasia, Eurasia, Africa, and North and South America.
I. cernua is a small sedge that can be common in boggy ground and around ponds in both freshwater wetlands and salt marshes, as well as among dune slacks and other brackish environments.