Cyperus vaginatus, commonly known as stiff-leaf sedge or stiff flat-sedge, is a perennial herbaceous plant that belongs to the sedge family, Cyperaceae. It is native to Australia. Stiff-leaf sedge typically grows to a height of 0.3 to 2 meters (1.0 to 6.6 ft) and forms dense clumps with a tufted habit. The plant features upright, stiff leaves and culms, and it blooms between November and February, producing inconspicuous green-brown flowers that are not particularly showy.

This sedge is valued for its ability to stabilize soil and for its use in water purification in constructed wetlands. It is also used ornamentally in water gardens and as a marginal aquatic plant. Stiff-leaf sedge thrives in full sun to part shade and prefers moist to wet, well-drained soils. It is relatively low maintenance but may require additional watering during dry periods in summer. While it is not known for significant pest or disease problems, it should be monitored where it spreads vigorously. CC BY-SA 4.0