Luffy uses his "Supreme King" Haki (also known as Conqueror's Haki) at various points, but he uses the advanced form—often called Advanced Conqueror’s Haki or Infusion—in Episode 1014 during his fight against Kaido.
If you are referring to the first time he uses the basic "Knockout" version of Conqueror's Haki, that occurs during the Marineford Arc (Episode 478), where he unknowingly knocks out the executioners preparing to kill Ace.
Luffy first uses Supreme King Haki (Haoshoku Haki) in Episode 389, though he does so unconsciously. His first conscious and intentional use occurs in Episode 518. 💥 Key Moments of Awakening
Luffy’s journey with Supreme King Haki transitioned from accidental outbursts to mastered combat techniques. 🌊 The Unconscious Outbursts
Episode 389: Luffy accidentally uses it to intimidate Motobaro (Duval's bull).
Episode 413: During his fight against the Boa sisters on Amazon Lily.
Episode 438: To save Mr. 2 (Bon Kurei) from wolves in Impel Down. which episode luffy use supreme haki
Episode 478: The most famous pre-timeskip moment. Luffy releases a massive burst at Marineford to stop Ace's execution, shocking the Admirals and Garp. ⚔️ Post-Timeskip Mastery
Episode 518: Luffy consciously uses Haki to take out Demaro Black’s crew on Sabaody Archipelago.
Episode 554: On Fishman Island, Luffy knocks out 50,000 Fishmen instantly.
Episode 716: A massive clash of Supreme King Haki against Donquixote Doflamingo.
Episode 852: His intense mental battle and Haki clash against Charlotte Katakuri. ⚡ The Advanced Stage: Infusion
In the Wano Country Arc, Luffy learns to go beyond just "releasing" Haki. Luffy uses his "Supreme King" Haki (also known
Episode 1028: Luffy discovers he can infuse his physical attacks with Supreme King Haki. This allows him to damage Kaido without making physical contact. 📖 Quick Reference Table Episode Number First Glimpse Taming Duval's Bull Greatest Outburst Marineford War First Conscious Use Return to Sabaody Mass Scale 50,000 enemies defeated Advanced Infusion Fighting Kaido on Onigashima
This is a fascinating question because it touches on a common point of confusion within the One Piece fan community. To give a direct and academically precise answer first: There is no episode in which Luffy uses "Supreme King Haki" because that specific term does not exist in the canonical manga or anime.
However, the intent behind your question is clear and worthy of deep analysis. You are asking about the pinnacle of Conqueror's Haki (Haoshoku Haki)—the ability to infuse one's willpower directly into attacks, a technique officially named "Infusion of Conqueror's Haki" (or Haoshoku no Haki no Idō).
This paper will clarify the terminology, trace the exact episodes where Luffy first demonstrates each major tier of Conqueror's Haki, and argue why the misunderstanding of "Supreme King Haki" is itself a valuable case study in how One Piece evolves its power system.
It is important to distinguish between "Basic Conqueror's Haki" and "Supreme/Advanced Conqueror's Haki," as Luffy has used the basic version much earlier in the series.
No episode of One Piece features Luffy using "Supreme King Haki" because the term is non-canonical. However, the technique most fans intend—the infusion of Conqueror's Haki into physical attacks—first appears in Episode 1071 as a single, instinctive blow, and is first mastered and sustained in Episode 1074. Luffy first uses Supreme King Haki (Haoshoku Haki)
For a definitive answer to the spirit of your query: Watch Episode 1074. It is the moment Luffy transitions from a Conqueror who merely intimidates to a "Supreme King" who fights as one.
It is important to note: Gear 5 (Episode 1071) is not Supreme Haki. Gear 5 is the awakening of Luffy's Devil Fruit (Hito Hito no Mi, Model: Nika). However, Luffy combines Gear 5 with his Advanced Supreme Haki in later episodes (1076+), creating the most powerful version of the character seen to date.
If you have been following the Wano Country arc of One Piece, you have likely heard a new, electrifying term floating around the fandom: Supreme Haki (officially known as Haoshoku Haki or the Color of the Supreme King). Fans are constantly searching: "Which episode does Luffy use Supreme Haki?"
The answer depends on which level of Supreme Haki you are asking about. Luffy has used basic Supreme King Haki since the Fishman Island arc, but the "new" power that breaks the internet—Advanced Supreme Haki (Infusion) —debuts much later.
Here is the definitive, episode-by-episode guide to Luffy's use of Supreme Haki.