Which fungus is the largest organism on Earth?

A honey fungus in Oregon’s Malheur National Forest is widely cited as the largest known organism on Earth. The organism, Armillaria ostoyae, covers about 965 hectares, or nearly 9.7 square kilometers, underground through a network of fungal threads. It was identified as a single genetic individual rather than a collection of separate mushrooms. Although hidden from view, it is a remarkable record-holder for size.