The Deku King is a character from The Legend of Zelda: Majora's Mask. The head of the Deku Royal Family, he is the ruler of the Deku tribe in Termina. His daughter is the Deku Princess. Together, along with a butler and servants, they live in the Deku Palace in the Southern Swamp.
Deku society in Termina is very different from that of the forest primitives in Hyrule, and has developed into a full-fledged civilization with an apparent social hierarchy.
When the Deku King's daughter goes missing, he immediately blames a small monkey (who was actually helping the Deku Princess) and locks him in a cage. Link sneaks through the Deku Palace, and ultimately reaches the inside of the imprisoned monkey's cage. Here, the monkey teaches Link the "Sonata of Awakening", and the Deku King takes this as further evidence that the monkey had a part to play in the kidnapping of the Deku Princess. Link is kicked out of the palace, while the monkey is left to meet his demise.
Link rushes to the Woodfall Temple and defeats Odolwa, resulting in the Deku Princess' rescue. Link stores her in a bottle and brings her back to the Deku Palace. Once Link delivers her to her father in the Royal Chamber, she becomes enraged at the Deku King's hasty decision to lock up the monkey, and the monkey is set free. The Deku King apologizes to the monkey, and the monkey forgives him.
In the end credits, the Deku King can be seen in the Deku Palace's Royal Chamber, accompanied by the Deku Princess, the monkey, and some Deku Palace Guards.