Herbs, perennial, rhizomatous, stout. Culms roundly trigonous, 300-500 cm × 15-45 mm, glabrous. Leaves bladeless. Inflorescences: spikes loosely cylindric, 10-20 × 6-10 mm; rays 40-100, drooping or arching, slender, 10-30 cm; 2d order rays 8-20 cm; bracts 4-10, ± erect, V-shaped, 3-8 cm × 4-15 mm; 2d order bracts 2-5, (1.5-4-16 cm × 0.5-2 mm; rachilla persistent, separating laterally, remaining firmly attached basally, wings 0.3-0.4 mm wide. Spikelets 6-30, slightly compressed, linear, ± quadrangular, 6-10 × 0.8-1 mm; floral scales 6-16, reddish beside 5-ribbed green medial part, white to hyaline near margins, ovate-elliptic, 1.8-2.2 × 1.2-1.5 mm, apex acute to obtuse. Flowers: anthers 0.8-1 mm (connectives prolonged beyond anther as red subulate appendage 0.2-0.5 mm, apex usually setose); styles 0.2-0.4 mm; stigmas 0.8-1.2 mm. Achenes pale brown, sessile, oblong, 0.8-1 × 0.4 mm, apex scarcely apiculate, surfaces puncticulate.

Fruiting summer. Stream banks, marshes; 0-30 m; introduced; Fla.; s Europe; sw Asia; Africa.

Cyperus papyrus is conspicuous in the field by its great height, leafless culm, and open, hemispheric inflorescence with drooping rays.

Ancient Egyptians, Greeks, and Romans prepared paper from the pith of the culms of Cyperus papyrus, which is abundant along the Nile River.