The Hundred Horse Chestnut (Italian: Castagno dei Cento Cavalli; Sicilian: Castagnu dê Centu Cavaddi) is the largest and oldest known chestnut tree in the world. Located on Linguaglossa road in Sant'Alfio, on the eastern slope of Mount Etna in Sicily — only 8 km (5 miles) from the volcano's crater — it is generally believed to be 2,000 to 4,000 years old (4,000 according to the botanist Bruno Peyronel from Turin). It is a Sweet Chestnut (Castanea sativa, family Fagaceae). Guinness World Records has listed it for the record of "Greatest Tree Girth Ever", noting that it had a circumference of 57.9 m (190 ft) when it was measured in 1780. Above-ground the tree has since split into multiple large trunks, but below-ground these trunks still share the same roots.
The tree's name originated from a legend in which a queen of Aragon and her company of one hundred knights, during a trip to Mount Etna, were caught in a severe thunderstorm. The entire company is said to have taken shelter under the tree.