One Piece is the name the world gave to all the treasure gained by the Pirate King Gol D. Roger. At least a portion of it once belonged to Joy Boy during the Void Century. The treasure is said to be of unimaginable value, and is currently located on the final island of the Grand Line: Laugh Tale.
The Great Treasure
At some point during the Void Century, a man named Joy Boy came across an island located at the end of the Grand Line. Here, he left behind a treasure of unimaginable value. Stories of this treasure on the final island peaked the interest of Gol D. Roger, and he took the World Government forbidding exploration of the island as evidence of it being real.
Only the members of the Roger Pirates that journeyed to the island know what exactly the treasure consists of. Upon arriving on the island and seeing Joy Boy's treasure, the Roger Pirates simply began to laugh. Roger described it as a "tale full of laughs", which gave him the idea to name the final island "Laugh Tale". Sometime after the Roger Pirates' discovery, the world at large would begin to refer to Roger's treasures as the "One Piece".
Before Roger was executed, he announced to the world that this great treasure could be claimed by anyone who could reach it, thereby starting the Great Age of Pirates.
The closest the Straw Hat Pirates have ever come to finding out the nature of One Piece was during the Sabaody Archipelago Arc, when Usopp tried to ask Silvers Rayleigh about it. However, Luffy stopped him on the grounds that learning about it from someone else would defeat the purpose of their adventures and that becoming the Pirate King would have little merit if he already knew anything about One Piece.
After decades of speculations and doubts, the treasure's existence was confirmed by Whitebeard with his last breath. He mentioned that "a grand battle will engulf the entire world" and "the world will be shaken to its core" when One Piece is found.
During the Wano Country Arc, Big Mom had an internal monologue expressing the idea that "some of" the One Piece might be located in Wano Country rather than Laugh Tale. This has yet to be elaborated on further.
Translation and Dub Issues
In the original manga, the term "One Piece" (ワンピース Wan Pīsu?) is often accompanied by an additional string of text translating roughly to "the great hito-tsunagi treasure" (ひとつなぎの大秘宝 Hito-tsunagi no Dai-hihō?), initially as a separate descriptor and later as a base-text directly glossed with the "One Piece" katakana.
The exact meaning of "hito-tsunagi" has not yet been clarified, and there are three possible readings:
- That it should be read as "一つなぎ" - a more or less literal Japanese translation of "(in) one piece".
- That it should be read as "人繋ぎ" - a phrase roughly translating to "the rope linking all men".
- That it should be read as "hitotsu-nagi" or "一つ凪" - a phrase roughly translating to "one sea at peace".
English translations - professional or otherwise - generally do not relay this text consistently, if at all. The Viz manga, for instance, refers to it as "[Gold Roger's] lost treasure" in Chapter 2, and as "greatest single treasure" in Chapter 507.
- Eiichiro Oda himself confirmed in an interview with Momoko Sakura that the One Piece is not something like "the journey itself was the real treasure" and that it is, in fact, a physical reward.
- Whitebeard stated in his final words that the world will be "shaken to its core" when the One Piece is found. Donquixote Doflamingo made a similar statement about the national treasure of Mary Geoise.
- One Piece Manga — Vol. 96 Chapter 968 (p. 3), Oden explains how the name "One Piece" came to be.
- One Piece Manga — Vol. 96 Chapter 967 (p. 17), The Roger Pirates arrive at Laugh Tale and find the treasure.
- One Piece Manga — Vol. 96 Chapter 966, Roger tells Whitebeard and Oden about the true final island.
- One Piece Manga and Anime — Vol. 52 Chapter 507 (p. 7-8) and Episode 400, Usopp asks Rayleigh about the One Piece's location.
- One Piece Manga and Anime — Vol. 59 Chapter 576 (p. 13-14) and Episode 485, Newgate confirms that One Piece exists.
- One Piece Manga — Chapter 1040 (p. 11-12).
- One Piece Manga and Anime — Vol. 1 Chapter 2 (p. 14) and Episode 1, Koby uses "ひとつなぎの大秘宝" to describe One Piece.
- One Piece Manga — Vol. 59
Chapter 576 (p. 14), Edward Newgate's death-speech at Marineford renders One Piece as
ひとつなぎの大秘宝. Afterward, most if not all in-story mentions of One Piece would follow the same format.
- While the kanji for the number one (一?) usually corresponds to the go-on pronunciation "ichi" (いち?), its kun pronunciation is in fact "hito" (ひと?).
- See also Zach Logan's analysis of both readings.
- Oda confirms that the One Piece is a reward.