Culms 5-40 cm. Leaves: basal sheaths somewhat glossy, bladeless; blades filiform, 2-15 cm × 0.25-0.5 mm. Inflorescences simple, 10-20 × 4-8 mm; proximal spikelets usually androgynous with 1-2 staminate flowers, 1 pistillate flower, and 1-3 scales; distal spikelets staminate, 1-flowered. Scales brown, obovate-circular, 3.5-5.5 mm, midvein distinct only near base, margins hyaline, apex obtuse. Anthers 2-3 mm. Perigynia brown, finely veined, 3.5-5.5 mm, margins connate near base. Achenes 2.6-4 mm.

Fruiting summer. Dry to mesic tundra; 0-3600 m; N.W.T., Nunavut, Yukon; Alaska, Colo., Wyo.; c, n Asia.

Kobresia sibirica, a local and variable species, is not yet fully understood. Some authors consider K. hyperborea and K. macrocarpa to be distinct endemic North American species; other authors include those and K. sibirica in the southwest Asian species K. schoenoides (C. A. Meyer) Steudel. In the Asian plants, the androgynous spikelets are reported as having 3 staminate flowers and no sterile scales.