Carex congdonii is a tussock-forming species of perennial sedge in the family Cyperaceae. It is native to parts of California.
The sedge has a turf-like habit with short rhizomes forming many stems. The smooth culms are located centrally and have a triangular cross-section with a length of . It has leaves with a reddish colour that are purple tinged basal sheaths. The M-shaped leaves have green blades with a width of and have long projections.