The Largest Living Organism Is a Honey Fungus Spanning 2,385 Acres in Oregon

The largest organism on Earth is not a whale or an elephant. It is not even visible most of the time. It is a single, vast network of fungal threads — a honey fungus called Armillaria ostoyae — living beneath 2,385 acres of the Malheur National Forest in eastern Oregon.

This single organism, identified by genetic testing, covers 9.6 km² (3.7 square miles), is estimated to weigh at least 35,000 tons, and is between 2,400 and 8,650 years old.

How Was It Found?

Forest pathologists first noticed clusters of dead and dying trees across the forest. When they sampled the fungal threads from soil and tree roots, they realized they were all genetically identical — meaning a single organism connected by countless interlocking threads.

What It Looks Like

• Most of the time, you cannot see it. The fungus exists as mycelium: thread-like white networks that spread through soil and roots
• The visible part — honey-colored mushrooms — only appears in autumn, briefly
• The fungus kills the trees it colonizes, eventually consuming them entirely
• Some scientists have argued it should be considered a "superorganism" rather than a single individual

Other Contenders for "Largest Organism"

• Pando (Utah): A clonal aspen forest covering 43 hectares, estimated to weigh ~6,000 tons
• Great Barrier Reef: Although a colony of millions of coral polyps, sometimes counted as a single organism
• Posidonia oceanica: A Mediterranean seagrass clone spanning 15 km

How Does Something Get So Big?

The Oregon honey fungus has had thousands of years and a stable forest environment. Each year, the mycelium expands incrementally outward, and once-separate colonies merged genetically. There is no central "control" — just a vast, distributed organism with no defined boundary except the forest's edge.