Presenting One of the Most Amazing Organisms On Earth. . . . . . So, Let's Get Started. Armillaria ostoyae (Largest Living Organism by Area) Image Credit: Wikipedia Armillaria ostoyae, also known as the "Humongous fungus", is the record holder of being the largest organism in the world by area. The areal size of Humongous fungus is about 2,400 acres i.e. 9.6 square km. It is very common in the western region of the U.S. These are the type of parasitic fungi which depend on other plants of survival. Due to the easy availability of land and nutrients, Humongous fungus has grown to this extent. Pando (Largest Living Organism by Mass) Image Credit: Wikipedia Pando is the world's largest organism in the world by mass of all time. It is so big that it covers about 106 acres of land and weighs about 60,00,000 kg. It's estimated age is about 80,000 years. Populus Tremuloides is a scientific name given to this giant. Pando also has a record o