Gunnera tinctora, commonly known as Chilean rhubarb or giant rhubarb (though entirely unrelated to true culinary rhubarb), is a massive, herbaceous perennial plant belonging to the family Gunneraceae. Native to the temperate rainforests of Chile and Argentina, the plant is famous for its colossal, umbrella-like leaves and striking architectural presence. The genus name Gunnera honors the 18th-century Norwegian botanist Johann Ernst Gunnerus, while the species epithet tinctora is Latin for "used for dyeing," pointing to its historical role as a source of natural tannins and colorants used in South American textile production.

The plant is exceptionally robust, featuring thick, fleshy rhizomes and massive rounded leaves that can easily span up to 2 meters across, borne on stout, prickly leaf stalks (petioles) that grow up to 1.5 meters tall. These stalks and veins are densely covered in bristly hairs and sharp prickles. Gunnera tinctora produces enormous, dense, cone-like flower spikes (panicles) ranging from reddish-brown to greenish hues, which give way to countless tiny, orange-red fleshy fruits. It thrives in damp, cool temperate environments with high moisture levels, commonly colonizing stream banks, ditches, and woodland edges where its canopy casts deep shade.

In traditional culinary and practical applications, parts of the plant have long been utilized by indigenous and local communities. The peeled young leaf stalks—known locally in Chile as pangue or nalca—are edible and possess a pleasantly tart, acidic flavor reminiscent of true rhubarb. They are frequently consumed raw with salt, added to salads, or stewed into jams and traditional beverages. However, older tissues and unpeeled stalks contain high levels of astringent compounds that can be irritating if improperly prepared. Beyond food, the tannin-rich rhizomes were historically harvested to extract brown and black dyes used for coloring wool and leather.

Nutritionally and biochemically, Gunnera tinctora is notable for its rich concentration of protective secondary metabolites. The plant tissues contain high levels of tannins, organic acids (such as oxalic and malic acid), and various antioxidant polyphenols. In traditional South American herbal remedies, decoctions of the root were sometimes employed as an astringent tonic to soothe gastrointestinal discomfort or applied topically to minor wounds. Outside of its native range, such as in parts of Ireland and the United Kingdom where it was introduced as an ornamental garden specimen, it has become a notoriously aggressive invasive species, forming dense thickets that crowd out native flora.