Tobi

, who posed as when first introduced, is a founder of Konohagakure, Akatsuki and the Uchiha clan. When he joined Akatsuki as Tobi, replacing Sasori, he was partnered with Deidara, revealing himself as Madara after Deidara's death. He has been recognized by Kisame Hoshigaki as once being the Mizukage of Kirigakure, although it is unknown when. He is the principal antagonist of the series, having being behind much of the conflict that has transpired in the Naruto world.

Background
Decades before the start of the series, Madara grew up in constant competition with his younger brother, Izuna Uchiha, who were both known as the most gifted members of their clan. Their competition led to both gaining the Mangekyō Sharingan, and, with it, they were able to take control of the Uchiha clan, Madara acting as its leader. Even by his clan's standards, Madara's chakra was unusually strong. Under his leadership, the clan conquered all they came across, but, over time, he began to lose his sight because of the Mangekyō Sharingan. To regain his vision, he took his brother's eyes (an act Madara said his brother had consented to), allowing him to continue to lead the Uchiha to prosperity.

In the years that followed, the Uchiha constantly clashed with the equally powerful Senju clan. To bring an end to the constant fighting, the leader of the Senju, Hashirama Senju, approached the Uchiha with an offering of peace. Although Madara never wanted peace with the Senju, the rest of the Uchiha wanted to end the fighting, and Madara had no choice but to go along with their decision. The Senju, the Uchiha, and all the clans they had conquered came together to form the village of Konohagakure. Against Madara's wishes, the villagers selected Hashirama as the village's First Hokage. Madara feared that Hashirama would oppress the Uchiha, and tried to rally support for challenging his leadership. Rather than help him, however, the Uchiha turned their backs on him, believing his only motives were due to pride and the desire for more power.

Abandoned by his clan, Madara left the village, later returning in order to challenge Hashirama in battle. They fought at the site that would someday be called the Valley of the End, where, although Madara called upon the Nine-Tailed Demon Fox, he was defeated, and was believed to have died. Madara faded into memory, and, in time, would found Akatsuki and become Kirigakure's Mizukage. He also appears to have fought Onoki the Tsuchikage at one point in his life as noted by the Current Raikage although the results of that battle were left unclear.

Twelve years before the start of the series, the Nine-Tails attacked Konoha. Although Madara denied having had any involvement in the attack, Itachi Uchiha and Minato Namikaze said that the Nine-Tails was under Madara's control at the time. A few years later, he infiltrated Konoha to try and rekindle the flames of war. He was found by Itachi first, who convinced Madara to spare the village in exchange for helping to wipe out the Uchiha clan for deserting him decades earlier. Madara complied, training Itachi and providing assistance. Itachi never truly trusted Madara, however, and kept an eye on him for the rest of his life. Madara also met with Danzō around the massacre, but did not see each other again until after Danzō fled the Kage summit.

Tobi
To keep in Akatsuki's shadow, Madara eventually took on the disguise of Tobi, giving orders to Pain in secret. He wears an orange, swirl-patterned mask that reveals only his right eye. When he trained Itachi, he wore a slightly different mask with black swirl-like patterns on it, and he had a longer hair cut than he does now. His hair is cut down completely from the days of Konoha's founding, and he wears a uniform consisting of a number of bolts and pins, which is usually concealed by his Akatsuki cloak.

While acting as Tobi, he is carefree and goofy, something that annoys most of the other members. Deidara, who believed all within Akatsuki should be serious and calm, was not pleased with Tobi's childish personality, and frequently attacked the latter in a comedic fashion when annoyed. Apparently, Madara is very committed to keeping his identity secret, as he has been seen keeping up his goofy appearance even when no-one was around (at least during the anime's filler arc). Kisame and Zetsu, on the other hand, somewhat appreciate Tobi's ability to brighten up a gloomy organization such as theirs. However, once his identity is revealed to everyone in Akatsuki, "Tobi" has abandoned his goofy nature and adopted Madara's personality.

Personality
Compared to his Tobi persona, Madara's true personality is considerably calmer and more serious, but he still has a habit of joking and disrespecting everyone around him. Despite his current limitations in battle, he is extremely arrogant, insulting even the strongest ninja to their faces and treating Akatsuki members as mere tools. There are only a handful of exceptions that he admires.

Madara has shown great ability in manipulating others to do his work for him. Minato believed that he was using Pain's ideology against him in order to control him. He similarly befriended Sasuke in order to get him to join Akatsuki by telling him about Itachi's past, even though he has an apparent interest in Sasuke and his abilities. He appears to have a somewhat twisted outlook with respect to this, often avoiding responsibility by claiming that people acted voluntarily when they were really coerced or manipulated by him.

Madara possesses an extreme hatred towards the Senju clan and Konohagakure, as he is a descendant of the elder brother who was passed over being the successor of the Sage of the Six Paths. This hatred was compounded when the Senju stripped the Uchiha of their powers and subdued them after the founding of the village, which chose Hashirama Senju to be Hokage over him. Madara admired Hashirama the most for his power, but loathed him the most for being a Senju. This hatred led Madara to a life dedicated to revenge. Madara believes that all Uchiha are destined to walk the same path of revenge against the Senju and Konohagakure, and that Naruto, who has inherited the Senju's Will of Fire, is fated to battle Sasuke, who has inherited the Uchiha's hatred, even if Madara himself must force them to do so.

Perhaps as a consequence of his old age, Madara seems to enjoy sitting down and taking his time with things, especially when telling stories.

Rescue Gaara arc
After the death of Sasori, Madara, as Tobi, appeared with Zetsu collecting Sasori's ring. He expressed interest in joining Akatsuki, believing that finding the ring would grant him membership. They then found Deidara's arm and the ring it wore, believing Deidara to be dead too. When Deidara appeared and demanded that Tobi give him his arm back, Tobi refused, prompting Deidara to try and choke him to death.

Three-Tails Arrival arc
Tobi was accepted into Akatsuki as Sasori's replacement and Deidara's new partner. He was assigned to capture the Three-Tailed Giant Turtle, and Deidara accompanied him. In the anime, during their search, they stopped to get a bite to eat at a dango shop, and Deidara waited anxiously for Tobi to remove his mask so that he could see what he looked like underneath, but he turned away, hiding his face. When he finished his dango, they split up and went in different directions. Tobi eventually found the lake and saw Sakura, Shizune, Hinata, and Ino on the lake using the Four-Corner Sealing Barrier. He then figured out that the technique was to seal the Three-Tails, and went after Deidara to inform him of his discovery. After Tobi watched Deidara kill two ANBU, he congratulated him. They both discovered the Three-Tails inside the lake. Deidara used his clay to make it appear outside, after which Tobi tried to convince Deidara to fight it in his place. The beast began chasing him, and Deidara used one of his bombs on it while it was distracted. The rest of the battle went unseen. Afterwards, Tobi started talking about how his jutsu was flawless, and now he understood why he had been assigned to the mission. Deidara retored that he wouldn't have got far without his clay. Tobi later fell asleep atop the Three-Tails after making another cheeky comment, much to the anger of Deidara, who "woke him up" by detonating a clay bomb next to him.

Hunt for Uchiha arc
Before sealing the Four-Tailed Monkey, Akatsuki learned Sasuke Uchiha had defeated Orochimaru. Once the sealing was complete, Deidara, angry that he had not got to kill Orochimaru, brought Tobi with him to kill Sasuke instead. They found and confronted Sasuke, and Tobi was given the job of providing assistance for Deidara during the battle. After some initial taunting from the duo, Sasuke surprised them both with his extreme speed and ran his sword straight through Tobi, apparently disembowelling him. Tobi then suddenly stood up again, complaining about the speed of the attack. The battle ultimately didn't go in Deidara's favor, so he used C0 in an effort to kill Sasuke at the loss of his own life. Zetsu reported to the remaining members of Akatsuki that Tobi had been killed too, prompting Pain to remark that he was easily replaceable.

It was soon revealed, however, that Tobi had survived, as he met with Pain and Konan in Amegakure. Tobi was now shown in a completely different light, and was revealed to actually be Madara, the real leader of Akatsuki. His entire demeanor and personality had changed during the appearance. He commented that Sasuke was developing nicely, and then instructed Pain to capture Naruto Uzumaki, the host of the Nine-Tails. He later appeared to distract the 8-Man Squad as Tobi while Sasuke fought with Itachi. The Konoha ninja had no success in striking him with their attacks, so Shino Aburame volunteered to fight Madara one-on-one. With his bugs, Shino was able to box-in and catch Madara, but Madara was able to escape from this as well. Zetsu then arrived to inform him that Sasuke had killed Itachi. Madara pointed out that he had known that this would be the outcome, and went to see Sasuke. Before leaving, his Sharingan was spotted by Kakashi.

Madara tended to Sasuke's wounds and, when he woke up, offered to tell him about Itachi. Madara tried to befriend Sasuke by removing his mask and revealing his Sharingan eye, something that caused Itachi's Mangekyō Sharingan to form in Sasuke's left eye and which made him use Amaterasu on Madara, who quickly retreated into the darkness of the cave. After stopping the black flames, Madara then appeared again with his mask back on, and began to muse about how Itachi never ceased to amaze him. After Sasuke asked what he was talking about, Madara revealed that Itachi had most likely set it up so that the sight of his Sharingan would trigger the Amaterasu he had sealed within Sasuke. After Sasuke complained that he was making no sense, Madara revealed that it was to protect him, and, when Sasuke still didn't believe him, Madara said how it all must sound crazy but assured him that he was telling the truth, and introduced himself as the man who had helped Itachi on that fateful night. He told Sasuke about the Uchiha clan's history, Itachi's secret life, and the lengths he had gone to keep Sasuke and Konoha out of harm's way. Sasuke, regretting that he had killed Itachi now that he knew the truth, resolved to destroy Konoha for forcing Itachi into the life he had lived.

Hunt for the Eight-Tails arc
Madara convinced Sasuke and the other members of Taka to start working with Akatsuki, the two groups having Konoha's destruction as a mutual goal. Before they could do that, however, he stated that Akatsuki needed the two remaining tailed beasts. Since Pain was still working on capturing Naruto, Madara sent Taka to capture the Eight-Tailed Giant Ox. After Taka left, Madara spoke with Zetsu, discussing Akatsuki's actions up to that point. He went on to say that, although they had lost five talented ninja in Akatsuki, all of their efforts had brought him closer to "making Sasuke his".

After Taka captured the Eight-Tails' host, Sasuke gave it to Madara for Akatsuki to seal. During the extraction process, it was revealed to be a fake. Madara was shown to remain silent, as Kisame commented that Sasuke had been fooled in the latter's attempt to capture the jinchūriki.

Invasion of Pain arc
After Nagato's death, Zetsu, after seeing (and "recording") everything that had transpired in Konoha, went back to the Akatsuki hideout to explain the situation to Madara. He pointed out that Konan was not coming back to Akatsuki, with Nagato being dead. Analyzing everything, Madara then sent Kisame to retrieve and capture the Eight-Tails, in which Taka had failed, as he said that he himself had "another matter to attend to".

Five Kage Summit arc
Anticipating Sasuke's betrayal, Madara intercepted Sasuke and his team on their way to Konoha. Madara revealed that Konoha had already been destroyed, and that Naruto had single-handedly defeated Pain. Madara also explained that Danzō had been made the acting Sixth Hokage, and was scheduled to meet with the other Kage on the matter of Akatsuki. After Sasuke left with Taka to kill Danzō at the summit, Madara explained to Zetsu that Nagato had betrayed him, as he had used Outer Path: Samsara of Heavenly Life Technique, and stated that it was supposed to be for him. Madara also explained that he had planned to sync Sasuke with the Demonic Statue of the Outer Path, and that Naruto had "thrown a wrench" into his plans. Madara then decided that it was time to come out of the shadows and to commence with the.

He is seen at the Land of Iron with the black half of Zetsu, ordering him to "begin". He later appears behind Naruto asking to have a chat with him when Naruto tries to attack him with a surprise Rasengan. Madara is then captured by Yamato's Mokuton jutsu and Kakashi appears behind him, threatening him with a Raikiri. Madara then goes on to say that none of their attacks will work on him and states again that he only wants to talk. Naruto then asks Madara about Sasuke, and Madara begins to tell Naruto of the man "eaten up by the ninja world's hatred and bitterness". He continues to tell Naruto, Kakashi and Yamato of the truth about Itachi and that Sasuke chose vengeance against Konoha on his own as his goal. Madara then tells them how Uchiha and Senju are descendants of Sage of the Six Paths and that Sasuke and Naruto were "chosen by fate". He tells Naruto that he will eventually have to fight Sasuke or rather, Madara will make him. He then states that he will use Sasuke to "verify the Uchiha clan's being." When Kakashi asks what Madara wants with the tailed beasts then, Madara reveals that it is "to become whole," before teleporting away. He is later seen in the five Kage's summit room, holding an unconscious Sasuke, telling everyone present there that he wants to talk to them about his Eye of the Moon plan.

Before Madara began, he teleported both Karin and Sasuke to a safe place, and told the Kage that he sent Sasuke to the summit as a means of improving his abilities and hopefully allow him to capture the Kage. Madara then explains that the Uchiha have a secret inscription that must be read in order of the Sharingan, the Mangekyō Sharingan, and finally the Rinnegan. The inscription told of how the Sage of the Six Paths saved the world from the original Tailed beast, the Ten-Tailed Beast, sealing the beast into himself becoming the first jinchūriki, and upon his deathbed divided the Ten-Tails power into nine separate beasts, and sealed it's body into the moon. Madara's plan is to use their collective power to combine once again make the Ten-Tails whole and make himself its jinchūriki. With it's power he would cast an, on the world, uniting the world in a permanent genjutsu.

After revealing his plan, he orders the remaining Kage to give him Naruto and Killer Bee or there would be unavoidable war, a war in which he would use the tailed beasts he already has. When they refuse, Madara declares the Fourth Great Shinobi World War. He then teleports after saying the next time they meet will be on the battlefield.

Madara then intercepted Danzō, who has fled from the Kage summit earlier, and claimed that they haven't met since the Uchiha Clan Massacre. After a fight has ensued, Danzō requested his subordinates to back him up as he releases the arm he stole from Shisui Uchiha.

Abilities
Most of Madara's abilities are still unknown. He is thought to be the strongest Uchiha to ever live, and one of the most gifted ninja in history. He was described as a "very powerful ninja" by Minato Namikaze himself. He has also been noted to have been born with particularly powerful chakra, which he states is the reason for his "stubborn refusal to die". Even the Nine-Tails mentioned that Madara's chakra is even more sinister than its own. One of the abilities he has actually displayed is his speed, which, as Tobi, was apparently his only claim to fame. To that end, Kisame commented "he is a good runner". Madara also appears to have immense strength, as he was able to stop a slash from Suigetsu's giant sword with a single arm. Onoki has alluded to Madara's full power in his prime by stating he shouldn't have to work from the shadows considering his power & skill.

He was armed with a giant kusarigama war fan attached to it during the time of Konoha's founding, fitting with his clan's name, which means "paper fan". He is also said to have been able to summon the Nine-Tails. It is unclear if this referred to the use of the Summoning Technique or if he could produce enough human malice to bring it to his location.

However, despite all the high-caliber power he has shown so far, Madara himself claims that the wound he received from Hashirama Senju has left him powerless, an empty shell of his former self.

Mangekyō Sharingan
During Itachi's fight with Sasuke, it was revealed that Madara Uchiha and his younger brother, Izuna, were the first members of the Uchiha to activate the Mangekyō Sharingan, and used its power to take over the clan. After going blind because of the use of the Mangekyō Sharingan, he implanted his brother's eyes into his own body. Madara then awakened a new "Eternal" Mangekyō Sharingan, a combination of his own and Izuna's Mangekyō Sharingan which led to him acquiring immortality. With it, Madara never had to fear the risk of losing his eyesight again. Madara's knowledge and mastery of the Mangekyō Sharingan gave him the power to forcibly subdue the Nine-Tails and the "Eternal" Mangekyō Sharingan allowed him to fight on par with Hashirama.

Teleportation
Madara shows the ability to completely avoid damage from most attacks. After being slashed across the midsection by Sasuke's sword, he collapsed, only to stand up again a few seconds later and complain about the speed of the attack. The same things occurred when Naruto hit him in the back with a Rasengan, where the attack literally phased through him, avoiding damage. His ability's consistency is confirmed when Sasuke attempted a Chidori on him, and, as predicted, he phased through Madara as he had done earlier.

Madara also shows the ability to travel long distances within relatively short timespans, escaping the final explosion created by Deidara and reappearing in Amegakure within a very short period. It was speculated by Kakashi that he uses spacetime Ninjutsu to instantly send himself or even parts of his body to different locations or some sort of void and then instantly bring them back. It is revealed that Madara can find the exact location of a person and warp himself to that place, stating that it is in his power. He has also shown the ability to teleport others, apparently to a separate dimension or area.

Past Speculation
Before Tobi was revealed to be Madara Uchiha, several fans hypothesized that he was Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted into Kakashi. They also have similar personalities, as well as the same hairstyles. The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito. Even though Tobi has been referred and revealed as Madara several times in the series, some fans still insist that Obito is somehow connected to Tobi or Madara.

Trivia

 * The phrase "Tobi is a good boy" has proven to be very popular among the Naruto community. Although not said by Tobi himself (Zetsu's white half actually uttered the phrase to his black half after stating Tobi's intentions of joining Akatsuki wasn't so simple to accomplish), many have found the comment to be rather hilarious and, as such, Tobi is depicted as a carefree child or a good-natured character in many fanmade art and videos on YouTube while incorporating the phrase. Many have altered the phrase, after Tobi revealing that he is Madara, saying "Tobi is a bad boy".
 * can be translated as "spots". Tobi can be translated as, or as . The latter translation connects Tobi with Taka through the Japanese proverb , meaning that an extraordinarily gifted child can be born from ordinary parents.
 * Tobi's first video game appearance is in Naruto Shippūden: Narutimate Accel 3.
 * According to the third Naruto databook (despite Tobi and Madara being the same person, the databook gives them separate entries):
 * Madara's hobby is falconry. As Tobi, his hobby is accompanying "Deidara-senpai".
 * Madara's favorite food is inarizushi, while his least favorite is roe.
 * Madara's favorite phrase is . As Tobi, his favorite phrase is given as.
 * Tobi's mask made a cameo appearance in the ending omake of Shippūden Episode 129 along with Baki's face and Haku's mask.
 * Tobi appears to have a liking for dango as seen in episode 99.
 * Madara makes a brief appearance at the end of the third Naruto OVA special, Naruto: The Cross Roads with Sasuke wearing his Akatsuki cloak. Currently in the Naruto: Shippūden anime, Taka and Sasuke working with Akatsuki has not yet happened.

Quotes

 * (To Pain and Konan) "The Sharingan's true power... this Uchiha Madara's power!" ("Sharingan no hontou no chikara ga... kono Uchiha Madara no chikara ga!")
 * (To Naruto while talking about Sasuke) "The Uchiha is a clan destined for revenge..."
 * (While addressing four of the five Kage) "In that case, I hereby declare... the Fourth Ninja World War."