A Leprechaun (Irish: leipreachán) is a type of fairy in Irish folklore, usually taking the form of an old man, clad in a red or green coat, who enjoys partaking in mischief. Like other fairy creatures, leprechauns have been linked to the Tuatha Dé Danann of Irish mythology.

If ever captured by a human, the Leprechaun has the magical power to grant three wishes in exchange for their release. Popular depiction shows the Leprechaun as being no taller than a small child, with a beard and hat, although they may originally have been perceived as the tallest of the mound-dwellers (the Tuatha Dé Danann).

The name leprechaun is derived from the Irish word leipreachán, defined by Patrick Dinneen as "a pigmy, a sprite, or leprechaun". The earliest known reference to the leprechaun appears in the medieval tale known as the Echtra Fergus mac Léti (Adventure of Fergus son of Léti).

The leprechaun is said to be a solitary creature, whose principal occupation is making and mending shoes, and who enjoys practical jokes. The leprechaun originally had a different appearance depending on where in Ireland he was found. Prior to the 20th century, it was generally held that the leprechaun wore red, not green.

The leprechaun is related to the clurichaun and the far darrig in that he is a solitary creature. Some writers even go as far as to substitute these second two less well-known spirits for the leprechaun in stories or tales to reach a wider audience. The clurichaun is considered by some to be merely a leprechaun on a drinking spree.

While many depictions state the Leprechaun to be extremely short, maybe only a few inches tall. There have been stories and tales of them being far taller.