Rhynchospora alba, the white beak-sedge, is a plant in the sedge family, Cyperaceae. It is a tufted herbaceous perennial around 50 cm tall, with white inflorescences that flower in August. The fruit of the sedge is a small achene with a characteristic beak-like cap. It is dispersed by wind or falls by gravity, leading to individuals existing in tight clumps. The species favours wet, acidic and nutrient poor soils, thriving in Sphagnum-dominated bogs, but also peaty grasslands. As such, it is often used as a positive indicator for bog and mire ecosystem health.

The species was first described by Linnaeus in 1753 under a different genus and name, Schoenus albus, but was subsequently reclassified into the novel genus Rhynchospora by Vahl in 1805. It has a wide range across the Northern Hemisphere, extending from the inland wetlands of North America, across Europe to the Korean Peninsula. Due to this large range, there is considerable variation between populations, and numerous varieties have been identified. The plant has few uses, though it is used as an ornamental in the UK.