King (Title)

King: A male monarchic ruler of the Kingdom. In the world of One Piece there are Royal Family who controls the local government.

All that I can do is human in nature... - Words of Nefertari Cobra


 * Wapol was the King of Drum, he is also the first royal king to appear in the series. He was soon overthrown and soon his Royal Guards leader Dalton became an new king, changing Drum to Sakura Kingdom


 * Nefertari Cobra was the king of Arabasta. He is the 12th line of the House of Nefetari, Princess Vivi is the be the 13th in the line.


 * Thelessa Lucas is the king of Ilusia


 * There is an unnamed king of Lyneel

Pirate King
However, there is a pirate king in the story. Pirate kings are people who are the strongest pirates of the seas, thus ruling the seas. To become a pirate king, one has to conquer and brave the whole Grand Line to find One Piece as a reward


 * Gol D. Roger was the first pirate king 22 years ago


 * Luffy wanted to be a pirate king also.