Carex debilior is a species of flowering plant in the sedge family Cyperaceae. The specific epithet derives from the Latin ' ("weak" or "feeble"), with reference to the species having weaker culms than Carex austrocompacta.
It is a tufted perennial, with filiform culms, growing to 15âÂÂ50 cm in height. The grasslike leaves are 5âÂÂ10 cm longer than the culms and 0.5âÂÂ1 mm wide. The slender inflorescence is 4âÂÂ7 cm long, with the lowermost 20âÂÂ30 flowers female, and the uppermost 5âÂÂ10 male.
The sedge is endemic to Australia's subtropical Lord Howe Island in the Tasman Sea. It occurs in low forest on and around the summits of Mount Lidgbird and Mount Gower at the southern end of the island.