|Enemies:|| Furnius (nephew)
|Location:||Fire Kingdom, Land of Ooo|
|Occupation:||King of The Fire Kingdom|
|Family:|| Flame Princess (Daughter)
Flame King's Brother (brother)†
Flame King is the ruler of the Fire Kingdom and Flame Princess' father. He first appears in "Incendium." Jake's mission was to impress him in order to make him let his daughter date Finn. After he thinks Finn kills Jake, he releases his daughter and promptly reveals that she is evil. He later appears in "Ignition Piont,," viewing a play which turns out to be Finn and Jake trying to warn him about an intended regicide. After he demands that Finn and Jake be executed for apparently disguising "treason" as a play, Torcho and Furnace (his nephews) are discovered as the true conspirators, and they reveal that Flame King killed his own brother (Furnace's and Torcho's father) so that he could take the throne.
He is much bigger than the other fire people. He wears a copper armor suit, carved with rhombus-shaped red gems in the armor's collar with a bigger pentagon-shaped one in the chest. The limb pieces have horizontal stripes with copper and brown colors and his hands are uncovered showing his hand-shaped flames. His head is similar to a giant fireball inside the armor, there are three holes in the flames that form the eyes and the mouth. His crown has five tips and a red gem in the middle. When traveling greater distances, he gets out of his armor as a flame and the armor follows him to the destination. Unlike his daughter, he does not have a humanoid body.
When traveling greater distances, he shifts out of his armor as a flame. When he reaches his destination, he merges with his armor at the new destination. He is acrobatic as he was able to jump from his balcony seat in the theater, do a full flip in the air and land perfectly on the stage in "Ignition Point."
He seems to be very aristocratic. He has a slightly impatient and demanding personality, stereotypical of royalty. He is also very protective of his daughter, Flame Princess. However, since she's left the Fire Kingdom he hasn't appeared to try and bring her home; she refuses to go back to him due to him locking her away in the lantern up until recent times.
He also understands himself as pure evil, having ascending to the throne by killing his brother and understanding that this evil nature exists in all in the Fire Kingdom.
- Flame King shares the same voice actor with Chaos from Final Fantasy, Keith David. Coincidentally, both characters are related with fire, destruction and are described as evil.
- In "Burning Low" it is implied that he may know Princess Bubblegum, as she was the one who had him put Flame Princess in her lantern.
- The reason he has his daughter kept in the lantern was because of her physical instability. Extreme romance would have resulted in disaster for Flame Princess and the world.
- Flame King's favorite thing in the world used to be koala bears.
- In "Ignition Piont" he reveals himself, as well as everyone in the Fire Kingdom, to be evil. He also confirms that Flame Princess is evil, but admitted that someone could possibly change her to be good.
- At the end of "Ignition Point" he uses his daughter's candles to leave the subliminal message of "evil" while she is sleeping.
- "Hot to the Touch" (mentioned)
- "Burning Low" (mentioned)
- "Ignition Piont"