In Irish mythology, Oilliphéist was a dragon-like monster.
The name is derived from the Irish oll, "great", and péist, "worm, fabulous beast, monster, reptile". The Scottish Gaelic variant is called Uilepheist.
In one story, the Oilliphéist cuts the route of the River Shannon when it hears that St Patrick has come to drive out it and its kind.
There is a comic addition to the story in which the monster swallows a drunken piper named Ó Ruairc (O'Rourke). The piper is either unaware of his predicament or is completely unperturbed and continues to play inside the monster's stomach. It becomes so annoyed with the music that it coughs him up and spits him out.