Mega Man X4 (ロックマンX4, Rockman X4), produced by Keiji Inafune, is the sixth game in the Mega Man X series. This game was originally released on July 31st, 1997 for the Sega Saturn in North America. Both the Sega Saturn and PlayStation versions were soon released simultaneously on August 1st, 1997 in Japan. The PC version was released in January 1st, 1998, and runs in operating systems after and including Windows 95. It was part of the Mega Man X Collection for the Nintendo GameCube and PlayStation 2, and the PlayStation version was also released in Singapore's AMK Hub on 2007. Artwork was done by Haruki Suetsugu.
- Mega Man X - X is the leader of the Maverick Hunters 17th Unit and an elite hunter. He has defeated Sigma several times in the past and is legendary among reploids. X is level-headed and rational, but hesistant to fight at times. During the Repliforce War, X befriends Double, who in secret is a spy sent by Sigma to monitor X's actions. When the remaining members of the Repliforce leaves to outer space to begin its new reploid nation, X goes to the Final Weapon, leaving Double in charge of the operation on Earth. Unknown to him though, Double abandons the Maverick Hunter Headquaters and finds X at the Final Weapon. He reveals his true purpose to X and transforms his body to combat the hunter. X defeats Double and proceeds to seek answers from General. Following General's defeat, X and Zero learn that someone, namely Sigma, has been pulling the strings and instigating the Repliforce War. After defeating Sigma and escaping the Final Weapon, X reflects on whether or not it is in his future to become a Maverick himself.
- Zero - Zero is an elite hunter and a close friend of X. In contrast to X, Zero is more aggressive and prefers to fight, given the situation. Like his friend, though, Zero can be calm and think rationally. Zero has had encounters with the maverick leader Sigma, in the past and present. Their rivalry spans as far back as when Zero was once known as the Red Maverick and Sigma was leader of the Maverick Hunter force. Zero has recently been haunted by visions of a mysterious figure who tells him to destroy. This figure is Dr. Wily, a mad scientist and Zero's creator. When the Repliforce is formed, Zero meets Colonel and the two become allies. Zero becomes fond of Colonel's sister, Iris. During the Repliforce War, their friendship is tested and eventually destroyed when the two eventually engage in combat. For the first time, after Colonel's death, Zero regrets having to fight. The second time this happens is when Zero unwillingly fights Iris and defeats her. With her death, Zero wonders if there is reason to go on and what it is that he is fighting for. Following General's defeat, X and Zero learn that someone, namely Sigma, has been pulling the strings and instigating the Repliforce War. Sigma is defeated and after escaping the Final Weapon, Zero reflects on the past that he once shared with both Colonel and Iris.
- Sigma - The mysterious being that meets in secret with General. He plans the destruction of the Maverick Hunters, and ultimately Earth, by manipulating the falsehood that the humans and reploids alike have misjudged the Repliforce. From that point on, Sigma instigates the Repliforce War, initiated by the Repliforce after General announces that he will build a new nation, one in which only Reploids can exist. The Repliforce is manipulated into developing the Final Weapon, a means of which the Repliforce would chronicle the first step in its independence. Sigma would later attempt to use the Final Weapon to destroy Earth, but is defeated once again by X and Zero. During the entire conflict, Sigma employs Double as a spy to watch X's every move.
- Colonel - The second in command of the Repliforce, Colonel is loyal to General in every respect and shares General's sentiment that the Repliforce must have its independence. Colonel is a very proud soldier; his pride prevents him from disarming and going with the Maverick Hunters for questioning following the attack on the Sky Lagoon. Though he is a friend of Zero, it is the Maverick conflict that drives a wedge between his friendship with Zero. Colonel has dislike (and perhaps contempt) for X, which is made obvious after the attack on the Sky Lagoon.
- General - General is the leader of the Repliforce. He meets in secret with a mysterious, cloaked being (who is later revealed to be Sigma) who insists to him that the humans are only using the Repliforce (and all reploids alike for the matter). Following the destruction of Sky Lagoon, General is incensed by the matter of the Repliforce being labeled as mavericks. As a result, he declares independence and initiates the Repliforce War. Later, General engages in a battle against X and Zero and is eventually defeated. The battle leaves General in a physically damaged state. Upon defeating General, it is realized that the Final Weapon is being used by someone else. After Sigma's defeat, in a last ditch effort, General uses his own body to destroy the final Weapon.
- Cyber Peacock - was a cruel hacker who set out to destroy the global information network, and used his hacker abilities to read X's data as he progressed through cyberspace. He found X's potential limitless, but remained confident in his ability to win over the Hunters right up until he was defeated.
- Frost Walrus - A member of Repliforce, Frost Walrus is known for his short temper and violent attitude. He can generate ice in various sizes. When the conflict arose between the Repliforce and the Maverick Hunters he was tasked with protecting a snow base that was developing a new weapon. Annoyed by X and Zero's presence in the snow base, Walrus fought them, but he was defeated and the weapon was destoyed.
- Jet Stingray - A leader in the Marine Corps branch of the Repliforce, Jet Stingray's unit destroyed a nearby city and he fled to a Marine Base somewhere near the decimated city. He can generate Stingray drones that attack ground based enemies. A chase took place at the Marine Base, where X and Zero eventually confronted Stingray and defeated him.
- Magma Dragoon - Dragoon was the leader of the Maverick Hunters 14th Unit, but betrayed the Maverick Hunters (thus going maverick) when Sigma convinced him that doing so will grant him his secret desire to combat X and Zero. He can project fire and and perform various moves related to fire. Dragoon took control of Egregion, resulting in the destruction of Sky Lagoon. His actions led him to occupy a volcano, where he was confronted and defeated by X and Zero. After his defeat, Magma Dragoon tries to tell the hunters why he took part in such acts, but dies shortly afterward.
- Slash Beast - Slash Beast is the leader of a unit in the Repliforce. Beast has the ability to project bi-directional crescent blasts at his opponents and can peform various other attacks. His unit was tasked with protecting the supply of goods on a military train. When Beast's unit and the military train was destroyed by X and Zero, he challenged them to a fight and was defeated.
- Split Mushroom - Split Mushroom is a maverick who can manipulate to a degree electric powers and has the ability to generate multiple replicas of himself using pure energy, an ability referred to as Soul Body. He used the Repliforce War as an excuse to cause havoc, having fun with every minute of it. When confronted by X and Zero, he refused to reveal who his commanding officer was (which was Sigma), but did say that he was ordered to terminate X. He failed to accomplish this though, and was destroyed.
- Storm Owl - Storm Owl is the leader of an elite unit within the Air Force branch of the Repliforce. He can generate long range blasts, use the Double Cyclone, and and manipulate the wind. When X and Zero destroyed his unit, he was enraged that his unit was destroyed and more enraged that the Repliforce was labeled a maverick force. He fights X and Zero and is defeated.
- Web Spider - Web Spider is a Guerrilla warfare expert who worked with Zero in the special #0 Unit until he turned to work for Repliforce. When confronted by Zero, the crimson Hunter begged his former ally to stop the violence and help end the coup, but Web Spider refused, forcing X and Zero to destroy him.
- Egregion - This giant dragon-like Mechaniloid is a war machine used by the Repliforce. When Magma Dragoon became a Maverick, he took control of Egregion and sent it to attack Iris and destroy the Sky Lagoon. X and Zero destroyed it, but not before it succeeded in bringing down the Sky Lagoon.
Following the third defeat of Sigma, Cain Labs issues an initiative to create a supplementary military force to complement the Maverick Hunters. This force, called the Repliforce, is a strict military regime led by General and his second-in-command, Colonel.
Six months following the inception of the group, Cain Labs finds its methods to be ineffective, questionable, and potentially dangerous in the defense against Mavericks. To make matters worse, General has been meeting behind in secret with a mysterious figure who insinuates that they are a threat to the jurisdiction of reploids alike, and plots the demise of the Maverick Hunters. Following an attack on the Sky Lagoon by the Maverick Egregion, General publicly announces that the Repliforce will attain independence from the humans and reploids, with his justification being that the Repliforce has been misjudged as a group of Mavericks.
- Blizzard Buffalo and Chill Penguin have small cameos in the beginning and middle of Frost Walrus' stage, where they can be glimpsed frozen in the background.
- The logo of Mega Man X4 appears as a billboard in Dead Rising 3's DLC mode Super Ultra Dead Rising 3' Arcade Remix Hyper Edition EX + α.
Producer: Keiji Inafune, Bamboo
Planner: Ohko, Mitsuru Endo, Hiroyuki Yamato
Programmer: Hisashi Kuramoto, Hiroki Bandoh, Syuichiro Chiboshi, Tomohiro Akizuki, Yuuji Hagiyama, Akihiro Kashimoto, Hideaki Motozuka
Object Design: Ikki Tazaki, Tsuyoshi Fujisawa, Nwo Hattori, Nottsu Man, Katsumi Toda, Obi Tomomi, Hayato Kaji, Nobuyoshi Mihara
Scroll Design: Natsue Ueda, Shimoyan, Mayumi Yoshioka, J R, Kita‑One, Kentaroh Ono
Title Design: Ukabin
Illustrations: Manashi, Hyper Mino, Sensei, Toyozo, Hideki
Music: Toshihiko Horiyama
Sound Effect: More Rich
Voice Actor (Japanese): Kentarou Ito, Ryotaro Okiayu, Ryuzaburoh Ohtomo, Jin Yamanoi, Yūko Mizutani, Yasunori Matsumoto, Mugihito, Issei Futamata, Kazuo Oka, Mari Maruta, Osamu Hosoi, Takashi Nagasako, Toranori Yoshikawa, Hiroyuki Yoshino, Takeshi Aono
Voice Actor (Overseas): Ruth Shiraishi, Wayne Doster, Mark Hagan, Matthew Meersbergen, John O'Corner, Jermy Felton, Michelle Gazepis, Charlie Fontana, Issei Futamata, Kazuo Oka, Mari Maruta, Osamu Hosoi, Takashi Nagasako
Opening Theme - "Makenai Ai ga Kitto aru"
Ending Theme - "One More Chance"
- Words by: Goroh Matsui
- Music by: Tetsuji Hayashi
- Arranged by: Takahiro Tashiro
- Song by: Yukie Nakama
- Xebec: Nobuyoshi Habara, Shinji Takagi, Shinichi Yamaoka, Hideyuki Motohashi, Meijyu Maeda, Rieko Nakai, Masahiro Satoh, Kanami Sekiguchi, Minoru Ueta, Ryota Niino, Miho Asano, Masakazu Kawazoe, Yuriko Ikehara, Yūko Kami, Nobuo Horii, Youko Ito, Shingo Adachi, Ryuji Fujita, Masaru Echigoya, Kaori Takahashi, Ayumi Tsukamoto, Mitsuko Sekimoto, Hiromi Aoki, Shizuko Kawabata, Kazuyo Ikeda, Natsuyo Ban, Masaki Kimura, Hisaaki Sakabe
- K Production
- Keison Production
- Koni Production
- Maki Production
- Trans Arts: Yukio Sugiyama, Hiroki Sekito, Haruhiko Tsumura, Saori Kibe, Hiroaki Matsuzawa, Tomohiro Baba, Chisato Asai, Takahiro Wada
- Production AI: Yoshimi Umino, Hachidai Takayama, Fumie Kawai, Fuyuki Sakanoue, Megumi Ogawa, Yukiko Ogawa, Nobuko Akutsu, Tomoko Takamura, Motoko Iwahashi, Saori Ishibiki
- Bandai: Katsuhiro Izumi, Takeshi Inoue
- ...and All Capcom Staff