Culms 20-35 cm × 0.3-1 mm. Leaves: apex of distal leaf sheath subacute to narrowly acute, tooth to 0.3(-1.1) mm. Spikelets narrowly lanceoloid, 3-12 × (1-)2-2.5(-4) mm, apex acute; floral scales 25-100, 10-12 per mm of rachilla, orange brown to stramineous, ovate, 1.5-2 × 1 mm, midribs mostly keeled, apex acute or narrowly rounded in proximal part of spikelet. Flowers: perianth bristles 6-7, brown, stout, the longest equaling or exceeding tubercle; stamens 2-3; anthers brown, 0.3 mm; styles 2-fid. Achenes 0.9-1.1 × 0.6-0.8 mm. Tubercles deltoid, 0.25-0.5 × 0.5-0.7 mm, 1/2-2/3 as high as wide, 1/4-1/2 as high and 2/3-4/5 as wide as achene. 2n = 10.

Fruiting summer to fall. Fresh shores, stream beds, pine woods, disturbed places; 0-400 m; Ark., Calif., Kans., La., Mo., Okla., Tenn., Tex.

Some collections of Eleocharis lanceolata from Tennessee appear to be intermediate with E. obtusa. The California record is an introduced rice-field weed collected in 1949.