Might Guy is one of the supporting characters in Naruto. Fansubs have often dubbed his name as Maito Gai, a direct and unaltered transliteration of the character's name, but the second official Naruto data book (Hiden: Tō no Sho) states his name as Might Guy. The English version of the anime and manga both use Might Guy as well.
In the Shonen Jump magazine, Viz rendered Guy's name as "Mighty Guy" in some of the earlier chapters; this was changed back to "Maito Gai" in most of the graphic novel stories and later changed to "Might Guy" when the guidebooks were released.
The name "Might Guy" is a joke aimed at the "hot-headed hero" archetype that appears in many movies and anime. Guy's appearance and mannerisms are similar to Bruce Lee's.
Might Guy is the extremely zealous leader of Team Guy, consisting of Rock Lee, Neji Hyuga, and Tenten. Known for his thick eyebrows, green jumpsuit, and shiny bowl haircut, Guy often refers to himself as "Konoha's Prideful Green Beast" (Konoha no Kedakai Aoi Mōjū; aka. "Konoha's Noble Green Beast"). Guy's favorite foods are super-spicy curry rice and curry udon, though he finds it impossible to dislike food. His favorite phrase is "Bursting with youth!"
Guy is on good terms with all of his students, though seems to have a particular interest in Lee, who reminds Guy of himself when he was younger, in that they were both considered to be losers and have had to earn everything through hard work. As such, Guy puts much more interest in Lee's training than Neji's or Tenten's, continuing to train Lee long after the others have given up for the day. Because of this, and due to Lee's unyielding desire to master the art of taijutsu, Guy has taught Lee a number of dangerous and forbidden techniques, giving the stipulation that Lee can only use them under specific circumstances. Although Guy knows of the dangers that teaching the techniques to Lee entails, Guy wishes for Lee to be able to prove himself to be a splendid ninja, and as such turns a blind eye to the repercussions.
Guy believes that "hard work without believing in yourself is worthless", and as such trains by repeatedly jumping sideways and hitting mitts in an effort to better himself. Guy, and by extension Lee, lives his life by his own "My Rules" philosophy, which involves setting tougher goals for failure so something good comes of it. For example, he vowed to walk 500 laps around Konoha on his hands if he lost a contest with Kakashi, and proceeded to do so upon losing, even though people stopped paying attention eventually. Lee's willingness to train in the same manner as Guy seems to have caused him to surpass his master's stamina, as by the end of Part I Guy has difficulty keeping up with Lee, lamenting that he is not as youthful as he once was.
Guy is the self-proclaimed rival of Kakashi Hatake. Kakashi, however, is indifferent to their rivalry, which annoys Guy to no end. Guy randomly challenges Kakashi to contests of skill, and has a acquired a record of 50 wins and 49 losses in doing so. Given that the contests that make up this figure are so varied (ranging from Rock, Paper, Scissors to sumo-wrestling), this it is not much of an achievement on Guy's part. Nevertheless, Guy is proud of his record. In his rivalry with Kakashi, Guy has developed an effective counter against Sharingan users: by focusing on their feet, Guy can both predict the movements of the enemy and negate the Sharingan's necessity of having eye-contact. Currently, Guy is the only ninja who can use this technique.
Guy has many mannerisms unique to him in the series that are meant to be seen as corny and old fashioned, a reference to common clichés of "youth" (seishun) anime. He is best known for his "nice guy pose", which consists of giving a thumbs up, winking, and smiling with teeth so white they give the proverbial "ping". This action is often used by both Guy and Lee to indicate commitment to a statement they had just made, their highest form of a promise. Guy's teacher-student relationship with Lee also carries distinct attributes, such as when Guy will punch Lee for a slight infraction of a rule. After Guy assigns Lee an arduous training task as punishment, meant to recapture Lee's focus and discipline, the two may then burst into tears and embrace, in brief regret for the strong blow Lee was given.
Guy specializes in using taijutsu, and is able to use many powerful taijutsu techniques. By his "My Rule" Guy has gained a strong body, by constantly training himself, and constantly pushing his own limits, allowing him to utilize the style known as Strong Fist a taijutsu skill that focuses on creating external damage, opposing to the Hyuga style known as Gentle Fist, that focuses on internal damage. Amongst others has his Taijutsu skills led to the development of his signature move known as Dynamic Entry (Dainamikku Entorii; literally "Dynamic Entry") an attack where he uses a flying kick to catch his enemy of guard, usually by distracting them with a thrown Kunai to change their attention away from him.
Like his student Rock Lee, Guy is able to utilize the Eight Gates (Hachimon; English TV "The Eight Inner Gates")(a feat that is difficult for even the most talented ninja) and has shown the abillity to open at least six of the eight gates. During his fight with Kisame Hoshigaki he opened the sixth gate and utilized the Morning Peacock, a technique so fast that his hand was set a blaze by sheer speed and friction. However since opening the gates can cause sever damage to the users body, Guy has, like he has told Lee, decided that he will only open the gates if it is life-or-death situations or protecting someone dear to him.
While he is capable of using ninjutsu and genjutsu, he tends to choose not to, even going so far as to use regular disguises instead of the Transformation Technique. In the few instances that he has used ninjutsu, it has always been offscreen, such as when he summoned Ninkame prior to his first appearance. Despite his apparent decision to only use taijutsu, Guy is a talented ninja, graduating from the Academy at age 7 and becoming a Chunin at age 11. Itachi Uchiha has on different occasions warned others against underestimating Guy. Given that Itachi and his accomplices are extremely dangerous ninja, such a warning is an indicator that Guy is an excellent combatant.