The Leprechaun, also known as the Clauricorn, is a magical creature that lives exclusively in Ireland. It reaches a height of six inches and can make clothing out of leaves. They alone of the Little People are able to speak the human language.
Leprechauns bear live young the same way humans do, and live in woodlands, where their favourite food, leaves, are abundant. They often intentionally attract Muggle attention and therefore often appear in Muggle literature and art.
They also produce a realistic substance not dissimilar to gold, which vanishes after a few hours to their great amusement. Ron Weasley, however, did not find this very funny as he used this gold to pay Harry Potter back for a pair of Omnioculars the latter had bought him.