The series begins with the execution of Gol D. Roger, a man known as the King of the Pirates (海賊王 Kaizokuō?). Just before his death, Roger announces that his treasure, the One Piece (ひとつなぎの大秘宝 (ワンピース) Wan Pīsu?), will be up for the taking, causing the Great Pirate Era (大海賊時代 Dai Kaizoku Jidai?) to begin. As a result, countless pirates set out to the Grand Line to look for the treasure.

Twenty-two years have passed since Roger's execution, and Monkey D. Luffy, a young pirate inspired by his childhood idol and powerful pirate Red Haired Shanks, has since set off on a journey from the East Blue Ocean to succeed Roger and find the legendary treasure. In an attempt to organize his own crew, the Straw Hat Pirates, he befriends a swordsman named Roronoa Zoro and together, they sail off to find the One Piece. They soon meet Nami, a navigator and thief; Usopp, a sniper and a liar; and Sanji, a womanizing chef; leading to confrontations with Buggy the Clown, Captain Kuro and Don Krieg. Later, Luffy encounters Arlong, a fishman and member of the former Sun Pirates who thinks that fishmen are superior to humans. After Luffy defeats Arlong, Nami joins Luffy's crew and theNavy places a bounty on Luffy's head. After making their way through the Grand Line, the group meets Nefeltari Vivi, a princess who wants to help save her country, the Alabasta Kingdom, from the crime syndicate Baroque Works. They later befriend the doctor and anthropomorphized reindeer Tony Tony Chopper while in Drum Island.