Caespitose perennial, 40-90 cm; with tillers. Stem 2.5-4 mm diam., obtusely trigonous, smooth. Leaves equalling or longer than stem; sheaths up to 20 cm, yellow-brown, often with reddish tint, soft, mouth margin somewhat concave; blades to more than 80 cm, 4-7 mm wide, greyish green, keeled, margins slightly revolute, margins and keel smooth or slightly scabrous, apex long-attenuate, trigonous, scabrous or nearly smooth. Inflorescence a rounded anthelodium, 8-10(-20) cm diam., primary branches 5-10, up to 10 cm, spreading, bracts 3-5 foliose, up to 50 cm; secondary anthelodia up to 5 cm diam., rounded with 3-5 bracts up to 30 mm; tubular prophyll up to 15 mm, yellow-brown often with reddish tint, bi-nerved, nerves with flat, scabrous arista up to 4 mm; tertiary anthelodia may be present; cluster of spikes 7-16 mm, nearly globose, with from c. 30 to more than 50 spreading, spirally arranged spikes, occasionally two sessile closely together. Spikes 5-7.5 x 0.5-0.8 mm, terete, brown, with 7 glumes, lowest sterile, next three fertile; rachis widely winged; glume-like bract c. 1 mm, brown, acute; glume-like prophyll c. 0.8 mm; glumes 2-3 mm, with rounded back, brown or reddish brown, mid-nerve ending in rounded apex, sides nerved, margins narrowly scarious. Stamens 2. Nut 2.3-2.4 x 0.3-0.4 mm, trigonous, slightly curved, plano-convex, brown, with persistent style-base c. 0.4 mm, finely reticulate and papillose.

Distribution: From Pakistan and India to China and Taiwan, Malaysia; intr. to Reunion and Mauritius.

Fl. Per.: September-November.

Swamps; also weed, especially in rice fields.

Mariscus compactus (Retz.) Boldingh, Zakfl. Java: 77. 1916; Druce, Rep. Bot. Exch. Club Brit. Is. 1916: 634. 1917; C. dilutus Vahl, Enum. Pl. 2: 357. 1805; C. spinulosus Roxb., Fl. Ind. 1: 207. 1820; Mariscus micocephalus Presl, Reliq. Hank. 1: 182. 1830; C. B. Clarke in Hook.f., Fl. Brit. Ind. 6: 624. 1893; Koyama, Fl. of Taiwan 5: Pl. 1344. 1979 (as M. compactus). U. Kühn, in E. Häfliger, ed., Monocot weeds, 53. 1982 (as M. compactus).

Cyperus compactus is a sedge of the family Cyperaceae that is native to the South East Asia, Madagascar and northern Australia.

In Australia it is found in the Kimberley region of Western Australia as well as parts of the Northern Territory and Queensland.