Phoracantha semipunctata, commonly known as the Eucalyptus longhorned borer, is a species of beetle belonging to the family Cerambycidae. It is native to Australia and is known for its distinctive long antennae and elongated body, reaching up to 30 millimeters in length. The adults are black with yellow markings and feed on the bark of various species of eucalyptus trees, causing damage to the wood. The larvae bore into the tree trunks, creating tunnels that can weaken the tree's structure.