The King of the Cats (or The King o' the Cats) is a folk tale from the British Isles. The earliest known example is found in Beware the Cat, written by William Baldwin in 1553, though it is related to the first century story of "The Death of Pan". Other notable versions include one in a letter written by Thomas Lyttelton, 2nd Baron Lyttelton, first published in 1782,M. G. Lewis told the story to Percy Bysshe Shelley in 1816, and a version was adapted by Joseph Jacobs from several sources, including one collected by Charlotte S. Burne.Walter Scott reported that it was a well known nursery tale in the Scottish Highlands in the eighteenth century. It can be categorised as a "death of an elf (or cat)" tale: Aarne–Thompson–Uther type 113A, or Christiansen migratory legend type 6070B.
A man travelling alone sees a cat (or hears a voice), who speaks to him, saying to tell someone (often an odd name, presumably unknown to the character) that someone else (normally a similarly odd name) has died, though other versions simply have the traveller see a group of cats holding a royal funeral. He reaches his destination and recounts what happened, when suddenly the housecat cries something like "Then I am the king of the cats!", rushes up the chimney or out of the door, and is never seen again.
In William Shakespeare's Romeo and Juliet, Tybalt is referred to by Mercutio as "Prince of Cats", and though this is more likely in reference to Tibert/Tybalt the "Prince of Cats" in Reynard the Fox, it demonstrates the existence of the phrase from at least the 16th century in England.