A boy named Monkey D. Luffy, inspired by his childhood hero "Red-Haired" Shanks, sets out on a journey to find One Piece, the legendary treasure of the King of the Pirates, Gold Roger. To accomplish this, he must reach the end of the most deadly and dangerous ocean: The Grand Line.

Luffy captains the Straw Hat Pirates first through the sea of East Blue and then through the Grand Line. He follows the path of the deceased King of the Pirates, Gold Roger, from island to island on his way to the great treasure One Piece. On his way his crew grows to have a swordsman, a navigator, a sniper, a cook, a doctor, an archaeologist, a shipwright, and a musician.

During the course of the story, the crew contend with both other less moral pirate crews and the Navy. The latter are the subordinates of the World Government, who apparently seek justice by ending the Golden Age of Pirates. Many background story elements involve the delicate balance of power between the World Government and the world's most powerful pirate crews.