The largest living organism in the world is a fungus called Armillaria ostoyae, also known as the "honey fungus." It spans across an area of approximately 2,385 acres (9.65 square kilometers) in the Malheur National Forest in the Blue Mountains of eastern Oregon, United States. The organism is estimated to be around 2,400 years old. Its extensive underground network of interconnected fungal threads, known as mycelium, allows it to spread and colonize vast areas.
Another notable contender for the title of the largest living organism is a grove of quaking aspen trees (Populus tremuloides) known as Pando. Located in the Fishlake National Forest in Utah, United States, Pando consists of genetically identical trees connected by a shared root system. It covers approximately 106 acres (43 hectares) and is estimated to be thousands of years old. While Pando is often referred to as a single organism, it is technically a clonal colony, with individual trees stemming from the same root system.
Both Armillaria ostoyae and Pando demonstrate the remarkable capacity of certain organisms to spread and persist across vast areas, making them fascinating examples of the size and longevity found in the natural world.