Eucalyptus regnans, commonly known as the mountain ash, is a species of tree native to southeastern Australia. It is one of the tallest tree species in the world, reaching heights of over 100 meters (328 feet). The tree thrives in cool, moist climates and is often found in temperate rainforests. The bark of Eucalyptus regnans is smooth and sheds in strips, revealing a pale, creamy trunk. Its leaves are lance-shaped and aromatic, containing essential oils. This species plays a crucial role in its ecosystem, providing habitat for various wildlife and contributing to the carbon cycle through its significant biomass.