Haohmaru is the star character of the series and is one of the series' most known characters (the other being Nakoruru). He is introduced in Samurai Shodown and continues to appear in every title of the series. His character origin was originally based around the famed swordsman, Miyamoto Musashi, a duelist who claimed to have never lost a match. He is visually modeled after Hyakkimaru from the manga, Dororo. Though he is a swordsman with no loyalties to any lord, Haohmaru has a "samurai spirit" which is often stressed in the series. He is also often accredited to defeating most of the series' villains.
In Gamest's 1997 Heroes Collection, Haohmaru was tied with Ukyo for 29th (out of 50) of the staff's favorite character rank. He was also voted as the second favorite character by the development team and fans in Samurai Shodown II. According to the Q&A page for Neo Geo Battle Coliseum, developers admitted that no matter what the fans wanted, they wanted to include Samurai Shodown characters and made Haohmaru's inclusion one of their top priorities in development. He also makes regular appearances in the series' merchandise and has at least two action figures.

Story
At the age of fifteen, he challenged Jubei to a duel but lost due to lack of experience. Jubei, amused by the youth's bravado, brought Haohmaru to Nicotine so that he may gain proper training. Whilst living there, he also met and befriended Genjuro, fellow student and another orphan like himself.
Orphaned, Nicotine Caffeine spotted him and took him under his tutelage along with Haohmaru in his home. Both students were close friends yet Genjuro's hunger for power worried Nicotine. To test his students, he tempted them to fight over the treasured sword, Fugudoku. They were tested by facing off with a group of other fighters. In contrast to his friend, Haohmaru fought only until his opponent lost the will to fight and didn't give chase. After Genjuro left Nicotine's home, Haohmaru was rewarded with the sword. Encouraged by his master to further improve himself, Haohmaru travels the lands perfecting his sword skills, and searches for worthy challengers in the name of Shura.
During his many travels, Haohmaru trains Shizumaru and inspires Takechiyo. He guided both until he felt they had matured enough before continuing his journey. He will sometimes challenge them to a duel after a certain amount of time to test their skill and resolve.
In Warriors Rage, Haohmaru is a skilled and active swordsman at the age of forty-seven who is revered by many to be the "Legendary Swordsman". He learns that his adopted niece, Mikoto, ran away from the temple (her childhood home) and follows her to the cursed island of Riten Kyo. There, he grows aware of the evil entities at work there, and departs on a journey to stop the Razor Trio, as well as duel worthy opponents along the way. In his ending, Haohmaru eventually reaches Mikoto at Riten Kyo and reveals her unspoken past to her.

Personality
Confident in his abilities, Haohmaru enjoys the thrill of fighting against strong opponents. Seeking enlightenment with each encounter, he constantly journeys in order to improve himself. As he gets older, he feels less inclined to fight and will try to avoid it if possible.
Outside of battle, Haohmaru is a crude but easy-going man, caring only for sake and food. He has a romantic interest in a simple girl named Oshizu ("O" added as a honorific prefix).

Fighting Style
He can use his sake jug to hit the opponent or to reflect projectiles. His trademark moves are Kougetsu Zan (Crescent Moon Slash), a crescent shaped uppercut, and Senpuu Retsu Zan (Whirlwind-Tearing Slash), a whirlwind projectile. In Samurai Shodown II, he also gained a somersault attack, which could cause massive damage upon crouching foes. When his style splits in Samurai Shodown III, his Slash form retains several strategies used in previous games, being a balanced and easy-to-master mid-ranged combatant. By contrast, his Bust form alters several moves, granting him access to aggressive close-combat fighting. His appearance in Warriors Rage also combined some elements from Genjuro's fighting style such as his stance and crouching strikes.

Voice Actors
* Masaki Usui - Samurai Shodown ~ Samurai Shodown IV, Edge of Destiny, Samurai Shodown VI (re-dub voice), Neo Geo Battle Coliseum
* Daiki Nakamura - 64 series, Warriors Rage; Capcom vs SNK 2
* Hiroyuki Koga - Samurai Shodown VI
* Shingo Katori - Samurai Shodown: Motion Picture
* Milton Lawrence - Samurai Shodown: Motion Picture (English voice)
* Bin Shimada - Samurai Shodown Dengeki drama CD series

Game Appearances
* Samurai Shodown
* Quiz King of Fighters
* Samurai Shodown II
* Samurai Shodown III
* Shinsetsu Samurai Spirits: Bushidou Retsuden
* Samurai Shodown IV
* Samurai Shodown 64
* Samurai Shodown 64-2 - his Shura/Slash form will not appear as CPU opponent
* Samurai Shodown!
* Samurai Shodown! 2
* Samurai Shodown: Warriors Rage
* SNK vs Capcom: Match of the Millenium
* Capcom vs SNK 2
* Samurai Shodown V
* Samurai Shodown V Special
* Samurai Spirits: Tenkaichi Kenkakuden
* Neo Geo Battle Coliseum
* Samurai Shodown: Edge of Destiny
* Samurai Spirits (pachinko)

Mobile Appearances
* Days of Memories (third and seventh titles) - unplayable
* Neo Geo Tennis Coliseum
* Samurai Spirits - Shimensouka
* Samurai Spirits - Makai Rineki

Cameo Appearances
* Nakoruru: Ano Hito kara no Okurimono
* Samurai Spirits Gaiden: Cham Cham

Anime Appearances
* Samurai Shodown: The Motion Picture
* Samurai Spirits 2: Asura-Zanmaden (OVA)

(Source: SNK Wikia)