- Honey mushroom, Armillaria ostoyae
- 965 hectare(s)
- United States ()
The largest living organism is a single gigantic specimen of honey mushroom (Armillaria ostoyae), discovered in the Malheur National Forest, Oregon, USA, which occupies a total area of 965 hectares (2,385 acres), equivalent to 1,350 soccer fields. The honey mushroom is well known for its glowing surface, caused by bioluminescent bacteria, although most of its tissue is around 1 metre (3 feet) underground, in the form of root-like mycelia. Its age is calculated to be at least 2,400 years old, but may be as much as 8,650 years old.
It also holds the record for the world's largest fungus.
The honey mushroom is estimated to weigh somewhere between 7,500 and 35,000 US tons (6,800–31,750 tonnes).
By contrast, the Great Barrier Reef (actually a series of 2,100 interconnected reefs) off Australia is considered the largest living structure; it has been formed over some 20 million years by the skeletal remains of billions of tiny marine organisms known as coral polyps.