The King of Thieves is a character in Adventure Time who has only appeared in the "City of Thieves." He is the king of the City of Thieves, but he is dead. It is unknown how long it has been since the people of the city have seen him, or if he even has any authority (although, due to his name, it could be that he was the ruler of the city and he took to a life of theft, which started thievery throughout the populace). Resting inside his rib cage is a treasure chest filled with gold coins and jewels, which Finn removes and takes with him. His tower is surrounded by a magical barrier that magically keeps thieves out (how he got in is never explained, though it is reasonable to assume the spell was cast over the tower while he was inside). The only entrance to his castle is a small window up high on a tall stone tower. He may be called the King of Thieves because he is very greedy and built the tower with the magical barrier to protect his gold.
The King of Thieves is a skeleton with a pair of purple gauntlets, a pair of golden shoulder plates, an eye patch with an emerald attached to it, and a crown with a crystal and a pair of long horns.
- It is unknown what species he belonged to when he was alive.
- There is a small game in the lower-left corner of his treasure chest.
- His eye-patch and resting place surrounded by stolen treasure draws comparisons to the pirate "One-Eyed Willy" from the film The Goonies.
- The fact that the chest is in the King of Thieves rib cage is a double entendre: Penny says Finn will "find the loot in the King of Thieves' chest," and the chest with the loot is in the chest of the deceased king's skeleton.