The largest living organism is a blue whale. The mycelium Armillaria ostoyae is the largest known living creature. It has a total diameter of 4 km and is made up of 1,000 fruiting bodies shaped like mushrooms. It is situated in the state of Oregon. Post navigation Most Impressive Rocks and Minerals 30 Best and Unusual Terrace Design Ideas 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25