⚠️ Spoiler Warning: This article contains spoilers up to the latest chapters of the One Piece manga, including events from the Final Saga.
The Straw Hat. It’s the most iconic piece of headwear in anime history — but is it just a hat? Japanese One Piece fans have been digging deep into the symbolism, history, and hidden meaning behind both Luffy’s treasured straw hat and the enormous frozen one sitting in Mariejois. What they’ve found connects Joy Boy, Ancient Weapons, Devil Fruits, and even the Yeti Cool Brothers into one sprawling theory.
Here is a complete breakdown of six major straw hat theories that have taken the Japanese fan community by storm.
Who Has Worn the Straw Hat? A Quick Rundown
Before diving into the theories, let’s establish the known lineage of the straw hat:
- 800 years ago: Joy Boy (likely — as the previous awakener of the Gum-Gum Fruit / Nika)
- 52+ years ago: Gol D. Roger
- 30 years ago: Shanks (passed down from Roger)
- 12 years ago: Monkey D. Luffy (entrusted by Shanks)
Others who have temporarily worn Luffy’s straw hat include Nami, Nico Robin, Sweetpea, and Otama. Luffy famously calls the hat his “treasure” — and given the enormous secrets hidden inside the Gum-Gum Fruit, it’s only natural to ask: is there something hidden in the hat itself?
Meanwhile, in Chapter 906 (Volume 90), the Holy Land of Mariejois was revealed to contain a massive, cryogenically frozen straw hat — apparently preserved with great care by Im. That detail alone launched a thousand theories.
Theory 1: The Giant Straw Hat in Mariejois IS Ancient Weapon Uranus
This is perhaps the most explosive theory of the six. In Chapter 1060, the kingdom of Lulusia was completely obliterated by a mysterious force — either Im’s personal ability or Ancient Weapon Uranus. This theory assumes the latter.
If Uranus has been in the World Government’s hands all along, two questions naturally arise:
- Why did Doflamingo desperately want the Ope Ope no Mi to access Mariejois’s “national treasure”?
- Why hasn’t Im used Uranus more aggressively before now?
The answer, this theory argues, is simple: Im couldn’t use it. Each Ancient Weapon is tied to a specific royal figure:
- Poseidon → Shirahoshi (Ryugu Kingdom)
- Pluton → Momonosuke (Wano Country)
- Uranus → Nefertari Vivi (Arabasta Kingdom)
The theory proposes that activating Uranus requires Vivi’s presence — possibly even her heart, which would make Doflamingo’s obsession with the Ope Ope no Mi’s “heart extraction” surgery a chilling piece of foreshadowing.
Further evidence comes from Im’s behavior in Chapter 908: Im destroys photos of Luffy and Teach, stabs a photo of Shirahoshi — but keeps Vivi’s photo intact. Vivi has since disappeared. The theory concludes: Vivi is currently with Im, serving as the key to Uranus.
This also explains a haunting line from the Sea Kings in Chapter 968, spoken 26 years ago: they speak of “two kings.” One is Shirahoshi. The other — born “in a distant sea” — would be Vivi, born 18 years ago in Arabasta. Roger understood this timeline and realized he was simply born too early.
As a bonus hypothesis, this theory suggests a dark chapter of the Void Century: Uranus was used to obliterate a great ancient kingdom, an Arabasta queen witnessed the devastation and refused to move to Mariejois — and in grief, raised the symbol of the sun in honor of what was destroyed.
Theory 2: Luffy’s Straw Hat Contains Joy Boy’s Haki
This theory focuses on the hat Luffy wears every day. If it was once worn by Joy Boy 800 years ago, could it still carry his Haki — specifically, his Conqueror’s Haki?
The strongest piece of evidence: in Chapter 1003, Kaido himself reacts to Enma’s “strange Haki” and recognizes it as Oden’s — centuries after Oden’s death. A sword can retain its wielder’s Haki. Why not a hat?
Additionally, when Roger first met Rayleigh, he was already wearing the straw hat and immediately asked him to help “turn the world upside down” — despite being unable to read the Poneglyphs and living before the age of Pirate King. How did Roger know? Rayleigh later hints that Roger could hear the “Voice of All Things.” Perhaps Roger heard the echoes of Joy Boy’s will through the hat itself.
When Roger reached Laughtale and realized he had arrived “too early,” he entrusted the straw hat to the next generation — Shanks. And Chapter 1054 offers a tantalizing visual: Luffy holds the straw hat up and, behind it, the sun shines through. Whether deliberate foreshadowing or not, it’s a striking image.
Theory 3: The Yeti Cool Brothers Were Created from Joy Boy’s DNA
This is the most creative theory in the bunch — and it connects several seemingly unrelated mysteries.
The Yeti Cool Brothers (Rock and Scotch) from Punk Hazard are some of One Piece’s most puzzling characters. Here’s what makes them unusual:
- Age: 25 years old — born the same year Roger reached Laughtale
- Height: 42.5 meters — twice the size of regular giants, but completely unlike Ancient Giants or any known giant race
- Blood type: S-RH− — one of the rarest blood types in the series, shared by only 11 characters including Sanji and Fisher Tiger
- S-RH− carriers tend to be twins/multiples, fish-men, hybrids, or artificially modified beings
The theory: Rock and Scotch are artificial creations by Dr. Vegapunk, built using Joy Boy’s lineage factor extracted from the frozen straw hat in Mariejois. Just as DNA can be retrieved from a hair follicle or the inside lining of a hat, Vegapunk may have extracted Joy Boy’s genetic material from the hat’s inner band.
Supporting this: Vegapunk’s Vivre Card timeline confirms he met the Five Elders in Mariejois during the MADS era. The Five Elders, unable to capture the Gum-Gum Fruit itself for 800 years, may have tasked Vegapunk with creating a counter-force to Nika using Joy Boy’s own lineage factor.
The theory goes further: Joy Boy and Luffy share the same face. If Rock’s face was ever clearly shown, it might look like Luffy — which is why Oda kept both brothers’ faces obscured. Their slender, distinctly human-looking faces match no known giant subspecies because they aren’t giants at all — they’re failed clones of Joy Boy’s Gigant form.
When Luffy activates Gear 5 (Nika), his body grows enormous. The frozen hat in Mariejois may have belonged to Joy Boy in that giant state — hence its enormous size.
Theory 4: The “One Piece” Is a Dress — And the Straw Hat Completes the Outfit
(Yes, this is the comedic theory. But hear it out.)
If the straw hat is the “national treasure” of Mariejois, and the treasure of Laughtale is the “One Piece” — what if “One Piece” is literally a one-piece dress? The straw hat and a sundress are, after all, the quintessential summer outfit for women.
- Evidence 1: Oda loves this kind of meta-joke humor
- Evidence 2: Portgas D. Rouge is shown wearing a one-piece dress in official art — possibly a wink from Oda
- Evidence 3: Doflamingo’s speech about the “national treasure” is immediately followed by Im looking at the straw hat — suggesting they are connected
- Evidence 4: Finding the “One Piece” symbolizes the Dawn of the world — the end of the long night
In all seriousness, the symbolic reading is this: the straw hat represents the sun, joy, and freedom. The “One Piece” represents a new world of light. Together, they form something complete — a Dawn that the world has been waiting 800 years to see.
Theory 5: The Straw Hat Sideways Looks Like the Letter “D”
A more visual and linguistic theory: tilt a straw hat on its side, and its curved brim forms a shape resembling the letter D.
The broader argument here ties the “D” in names like Monkey D. Luffy, Gol D. Roger, and Trafalgar D. Water Law to a real-world historical parallel: the French noble prefix “de” (as in Jacques de Molay, last Grand Master of the Knights Templar).
- The Knights Templar were unjustly destroyed by King Philip IV of France — just as the “D” clan’s ancient kingdom was wiped out by the 20 kingdoms that became the World Government
- Templar survivors became pirates and stonemasons — paralleling One Piece’s pirate culture and the Poneglyphs carved in stone
- The “D” is not an acronym for Dawn, Devil, or Destiny — it’s a family marker, a title of nobility from a fallen civilization
The straw hat, as a symbol of that civilization’s kings, literally carries the “D” in its shape.
Theory 6: Luffy’s Straw Hat Has Eaten a Devil Fruit
The final theory is the most speculative — but One Piece has already shown us that objects can eat Devil Fruits. Spandam’s elephant sword Funkfreed, the sword Shusui (before it was returned), and various weapons throughout the series have demonstrated this. Vegapunk himself confirmed it as a “new technology” he developed.
If Luffy’s straw hat was once Joy Boy’s, and Joy Boy came from a civilization as advanced as Egghead Island (or more so, per Shaka’s claim in Chapter 1065), then that ancient kingdom may have already mastered the technique of feeding Devil Fruits to objects.
What fruit might the straw hat have eaten?
- Fune Fune no Mi, Ancient Type, Model: Uranus — making the hat a vessel or key for the Ancient Weapon
- Kagi Kagi no Mi (Key Key Fruit) — making it a literal “key” to unlock the One Piece
That said, the timeline is a major obstacle: the “object Devil Fruit” technique was only developed “in recent years” by Vegapunk — well after Shanks gave Luffy the hat 12 years ago. Unless the ancient kingdom had already cracked this secret 900 years earlier, this theory requires a significant leap of faith.
Conclusion: So What IS the Straw Hat?
After six theories ranging from ancient weapons to comedy fashion, the most grounded conclusion is this: the straw hat is, at its core, a hat — but one soaked in history, Haki, and lineage factor. It was likely worn by Joy Boy himself, passed through Roger and Shanks to Luffy, and carries both the spiritual will and possibly the genetic blueprint of the man who first embodied the Sun God Nika.
The giant frozen straw hat in Mariejois is almost certainly Joy Boy’s — preserved by the World Government not out of reverence, but out of a desperate need to understand and counter the power it represents. And if the ancient kingdom’s kings wore straw hats as a symbol of the sun and freedom, then every time Luffy tips his brim, he’s carrying 800 years of revolutionary history on his head.
Whether it’s an Ancient Weapon, a Devil Fruit vessel, or simply the world’s most meaningful accessory — one thing is clear: that straw hat will matter when the final chapter arrives.