Tobi

The primary antagonist of the series. Madara, at the beginning posing as in the Akatsuki, formerly appeared to be Zetsu's subordinate. Madara became a full Akatsuki member after Sasori's death and afterwards wore the same ring as Sasori having recovered it after his death and taking his place as Deidara's partner. After Deidara's death, he revealed his real name and that he had been the one giving Pain orders, making him the true leader of the Akatsuki. Only Pain, Konan, Zetsu, and Itachi Uchiha and recently Kisame (who recognized him as the former Mizukage) knew his true identity. He is one of five people who can use the Mangekyo Sharingan, the other four being his younger brother Izuna Uchiha, Itachi Uchiha, Sasuke Uchiha, and Kakashi Hatake. Tobi (飛) can be translated as "jump", while Madara (斑) can be translated as "spots".

Background
According to Madara, eighty years ago, when shinobi were battling as individual clans, not as villages, among a countless number of them, two clans emerged as the strongest: the Uchiha clan and the Senju clan. Madara was also the first to activate the Mangekyo Sharingan. He had a younger brother, who was equal to him in every way and also awakened the Mangekyo Sharingan. Together they ruled over the Uchiha clan, with Madara taking the role as leader. But eventually Madara went blind, due to side effects of the Mangekyo Sharingan. During the final fight of Itachi and Sasuke, it is revealed that Madara took away his brothers eyes which killed his brother. Contrarily to what many believed, Madara claimed that his younger brother gave him the eyes voluntarily to protect the Uchiha clan. At some point in Madara's early life, by the decision of the entire Uchiha clan except for him, he formed an alliance with the Senju clan, Hashirama Senju's clan, and together with its leader, the future First Hokage, Madara founded Konohagakure.

However, when Hashirama was chosen to be the First Hokage of Konoha, Madara feared that the Uchiha clan would lose supremacy and he sought the help of the Uchiha in his challenge for leadership. The Uchiha clan, however, refused, believing he was greedy. None of the Uchiha would help Madara, and he decided to leave the village. Feeling hurt and betrayed, he came back and wanted revenge against Konoha which led to a legendary battle at the Valley of the End against Hashirama. During the battle, Madara used his Mangekyo Sharingan to take control of the Nine-Tailed Demon Fox and used it in a desperate attempt to kill Hashirama. Madara, however, was ultimately defeated and was presumed by most to have died after the battle. Madara fled, and was never seen or heard of again out in the public for decades. To commemorate the battle, two statues, one of Madara and the other of the Hashirama, were carved into the earth around the waterfall. It is for this reason that Naruto Uzumaki and Sasuke's fight at that location was noted to be ironic. Madara created the criminal organization known as the Akatsuki to look over problems. He hid behind the shadows and placed Pain as the figure-head leader, with Madara giving Pain orders from the background. Outside of Pain, the only members who are shown knowing Madara's position as the true leader are Konan, Kisame, Zetsu and Itachi. Itachi believes it was Madara himself that controlled the demon fox to attack Konoha, though Madara denies this, saying that the demon fox was a natural disaster. Nevertheless, when he came to destroy the entire village of Konoha in revenge, he met up with Itachi, who had already been assigned his mission to kill his clan. Itachi successfully talked Madara into only killing the Uchiha clan as long as he left the rest of the village alone. Madara also taught Itachi about the Mangekyo Sharingan, helping him by teaching him how to unlock its true power. After Itachi killed off the Uchiha clan because of orders from Konoha, Madara let Itachi into Akatsuki for unknown reasons. Itachi refers to Madara today as "a pathetic shell of his former self, no longer worthy of being called the greatest Uchiha." It has also been recently revealed that at some point after being presumably killed, Madara took the role of Mizukage.

Personality
Madara sometimes exhibits a very calm and serious personality and at other times he exhibits a playful disposition, especially when in the disguise of Tobi. He speaks with less formal diction, such as not using honorifics, and shows typically "villainous" arrogance. Despite this apparent arrogance, he is not above complimenting the abilities of Sasuke Uchiha and Naruto Uzumaki, if only for the interest of Sasuke's Sharingan and Naruto's Tailed Beast. Despite his villainous personality, during the first wars he wanted to protect the Uchiha clan and knew that the wars would eventually extinguish it, which is why, when the entire clan wanted it, he agreed on the peace treaty with the Senju clan.

Tobi
To keep in Akatsuki's shadow, Madara eventually took on the disguise of Tobi and was placed within Akatsuki as Zetsu's subordinate. As Tobi, Madara wears an orange mask, with swirls focused around the right eye, that covers his entire face outside of his right eye. Before wearing the swirl mask, Madara wore a similar mask, with markings across it which resembled the Hidden Mist Village's ANBU mask, covering his entire face but the right eye. However, the mask does not bear the symbol of the Hidden Mist Village. Furthermore, Tobi has several bolts or pins present on the arms of his uniform, obscured by his Akatsuki cloak. While acting as Tobi, unlike others within Akatsuki, Tobi is carefree and goofy, but Madara uses a very formal and correct manner of speech. While Tobi greatly respects his other members, referring to Deidara as Deidara-senpai in the Japanese version, most of the other members tend to get easily annoyed by Tobi. Deidara, who believes all within Akatsuki should be serious and calm, is not pleased with Tobi's childish personality, and frequently attacks Tobi in a comedic fashion when annoyed. Kisame and Zetsu, on the other hand, somewhat appreciate Tobi's ability to brighten up a gloomy organization such as theirs. As Tobi, Madara has not been seen wearing a forehead protector, probably to conceal his identity, though he already has a mask covering his forehead, so this could also be why it is not visible. Although, it stands to reason that since Madara hates Konoha, he probably refuses to wear the headband anyway, like Orochimaru and Sasuke.

Rescue Gaara arc
Madara is first introduced as Tobi alongside Zetsu collecting the rings of Deidara and Sasori. While Sasori's ring is collected, Deidara, who managed to live, appears and reclaims his own ring. After annoying Deidara three times, Deidara responds by comically choking Tobi with his feet. Using Sasori's ring, Tobi manages to join Akatsuki, though Zetsu claims it isn't as easy as collecting the ring.

Hidan & Kakuzu arc
Tobi, who by now has successfully joined Akatsuki, is partnered with Deidara and sent to collect the Three-Tailed Beast. After Deidara reveals that this is Tobi's mission, Tobi, panicking, is seen only running away from the Three-Tails in a comic fashion. After the battle, which goes mostly unwitnessed, Tobi triumphantly claims to have defeated Three-Tails in a single blow, though Deidara disagrees. Tobi later falls asleep atop the Three-Tails after making another cheeky comment, much to the anger of Deidara, who "wakes him up" by detonating a clay bomb next to him.

Hunt for Itachi Uchiha arc
Tobi is seen following Deidara, who is chasing Sasuke Uchiha, and eventually join Deidara's battle with Sasuke, though he does little besides laying mines for him and serving as a distraction. When Deidara prepares to use C4, Deidara orders Tobi to flee, though, while escaping C4, Tobi is later shown getting killed by Deidara's final explosion.

It is later revealed, however, that Madara lived, as he is seen ordering Pain in Amegakure just a few minutes after Deidara's death. Madara gives Pain the order to personally capture Naruto Uzumaki. Madara then travels to the Valley of the End on his own statue as Tobi, and while resting there, comments that Sasuke's Sharingan is growing more powerful.

Madara appears as Tobi to stop Naruto, Hinata, Yamato, Kakashi, Sakura, Shino, Sai, and Kiba from searching for Sasuke and Itachi Uchiha, and phases through all attacks the group sends, even a full-powered Rasengan from Naruto Uzumaki and a full ranged attack from Shino even after completely covered in bugs. Tobi continued to fight the 8-Man Squad until Zetsu arrived to tell him that Itachi had died, which was no surprise to Madara. Before he took his leave, the Sharingan, which he possessed, was spotted by Kakashi. Tobi and Zetsu arrived at Itachi's battlefield, to recover the bodies of the two brothers, before the 8-Man Squad caught up to them. Off in a cave somewhere, Sasuke is startled to see Tobi, who says he gave him some first-aid, and that Itachi had removed the seal. Madara then claims to know the truth about Itachi as he removes his mask revealing a glimpse of his Sharingan. In the next chapter, Sasuke is shown using Mangekyo Sharingan but it only appears in his left eye, using Amaterasu to attack Tobi. Tobi explains that Itachi gave all of his eye techniques to Sasuke, as a backup plan in case Sasuke ever met him.

He then continues by saying that Sasuke had to question him, calling it his mission and duty. Furthermore he began revealing that Itachi, risked all to protect the shinobi world, Konoha, and most of all, his little brother. He tells Sasuke about how the Senju clan and the Uchiha clan were rivals. When the Senju clan wanted to form an alliance with the Uchiha clan, Madara was the only one against it. He soon agreed and together they formed Konoha. For the position of Hokage, everyone in the village and the land of Fire chose Hashirama. Madara saw that the Uchiha clan was losing supremacy, and chose to oppose Hashirama. But no one among the Uchiha followed him. They despised him saying that he was greedy and stole his own brother's eyes to save himself. He left the village and bent on revenge challenged the village. Madara and Hashirama fought. Although Madara controlled the demon fox during the battle, he was defeated in the place now known as the Valley of the End, probably due to Hashirama's Tailed beast-suppressing jutsu. After the battle, he was presumed dead by most of the village. Madara then tells Sasuke the truth of Itachi.

Sasuke's Revenge
After the formation of Hawk, Madara removes his mask before Kisame Hoshigaki, who recognizes him as the former Mizukage. When Kisame recognizes him, he says he seems to know him and says he feels better knowing "you're the one who's pulling the strings". Kisame states that "when the planning began, Madara officially allied Akatsuki with them for their goal to destroy Konoha". Madara states that they will use the Tailed Beasts to destroy Konoha and will require Hawk to capture the Eight-Tailed Beast. Afterwards, Madara met with Zetsu to discuss the fate of the old Akatsuki members, and more importantly, how Madara now has Sasuke. He displays some gratitude toward the fallen members, stating that they wouldn't have gotten this far without them.

Madara later traveled to Pain and Konan's home where he learned of Jiraiya's death. He then questioned Pain's abilities which, only to receive a cold stare and lecture from Konan about her comrade's power. Madara then tells them about Sasuke going after the Eight-Tails, which he is sure Sasuke will accomplish and then leaves. Upon speaking with Sasuke following his descendant's success in capturing Kirābī, Madara made no comments regarding Sasuke's revelation that his plan was to destroy Konoha instead of merely Danzo and the two surviving members of Team Tobirama. Madara later seals the eight tails along with Zetsu and Kisame. However, the body turns out to be a tentacle to which Madara remains silent.

Abilities
Most of Madara's abilities are still unknown. But as he was regarded as the strongest Uchiha to ever live, it presumed he has mastered all of his clan’s jutsus and skills. Since the Uchiha clan is known for its fire techniques, it is also speculated that he knows advanced fire techniques as well. Considering he was once the Mizukage, it can be presumed he also has access to powerful water ninjutsu. Since he was young, Madara was regarded as incredibly gifted, not unlike that of Itachi Uchiha. He was also noted to have been born with a particularly strong amount of chakra, which he states due to his "stubborn refusal to die". His chakra was strong even for the Uchiha clan, who were known for having strong chakra. The demon fox mentioned that Madara's eyes are even more sinister than its own.

He was armed with a giant fan during the time of Konoha's founding, probably to fit with his clan's name, which means paper fan. It may also suggest that he had access to wind chakra and used the fan to enhance his fire jutsu similar to how Temari uses her fan. Madara’s prowess in battle has earned him a reputation rivaling that of the First Hokage, as he is referred to by Itachi as an "invincible immortal", yet he is also referred to as currently "a defeated dog". Madara is also the only known wielder of the technique of summoning the demon fox, a being so powerful that it almost laid waste to Konoha until Minato stopped it. Madara was the only person capable of taming the demon fox, which was said to only come where human malice collects and festers. He somehow tamed the demon fox by using the Mangekyo Sharingan.

Madara shows the ability to recover from debilitating or even fatal blows. After being slashed across the midsection by Sasuke's sword, he collapses, only to stand up again a few seconds later and complain about the speed of the attack, and later when Naruto hits him in the back with a Rasengan. The attacks literally phase through him, avoiding damage. He is also seen being hit by Itachi's Amaterasu but emerging unharmed. It may also be possible that he might have the same ability as Sasuke, to make the Amaterasu flames vanish or he could have just teleported the parts of his body that were hit. However, Madara's immortality may not be perfect as he suggested that if he hadn't kept some secrets from Itachi, he would have died by the Amaterasu technique Itachi implanted on Sasuke's Mangekyo Sharingan.

Madara also shows the ability to travel long distances within relatively short time-spans, escaping the final explosion created by Deidara and reappearing in Amegakure, then travelling to the Valley of the End all within a very short time span. It is speculated by Kakashi and Sakura that he uses space/time Ninjutsu to instantly send himself or even parts of his body to different locations or some sort of void and instantly bring them back. Kisame also comments "he is a good runner."

During his fight with Naruto and the rest of the 8-Man Squad, Madara demonstrated a mastery of space and time Ninjutsu that, as speculated by Kakashi and Sakura, surpassed even the Fourth Hokage. With it, he was able to take head-on a fully powered Rasengan by Naruto by having it phase right through him, and also when he escaped Shino's bugs even though they completely surrounded him.

During Itachi's fight with Sasuke, it was revealed that Madara Uchiha and his younger brother were the first members of the Uchiha to activate the Mangekyo Sharingan, and used its power to take over the clan. After implanting his brother's eyes into his own body, Madara then awakened a new "eternal" Mangekyo Sharingan. The "eternal" Mangeyko Sharingan is a combination of his own and his brother's Mangekyo Sharingan. It gave him access and mastery to his clans’s most consequential jutsus, including a “final and ultimate jutsu” as Itachi stated, along with untold amounts of power without the risk of losing his eyesight. Madara's knowledge and mastery of this powerful Dojutsu allowed him to fight on par with Hashirama and it gave him the power to forcibly subdue the demon fox. It was also thanks to Madara's knowledge of this Dojutsu that Itachi learned how to properly use his Mangekyo Sharingan. Madara appears to have immense strength, as he was able to stop Suigetsu's giant sword with a single arm.

Past Speculation
Before Tobi is revealed to be Madara Uchiha, several fans hypothesized that he could be Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted in Kakashi. Obito's eye replaced Kakashi's destroyed left eye in the manga-exclusive Kakashi Gaiden. They also have similar hair styles as well as the same blood type, "O". Also, they both act in the same goofy way. Half of Zetsu claims Tobi to be a good boy while Obito was a good boy. The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito.

Other speculations note a similarity between Pain's multiple bodies and the bodies summoned by Orochimaru's Summoning: Impure World Resurrection. The speculation is that Obito could have been reanimated or also had Madara's spirit implanted within him. This speculation is inherently flawed though, as neither of the techniques noted by fans were ever shown or meant to be used in the ways that fans speculated.

Fans also speculate that Madara could also be Danzo as many physical characteristics of Madara/Tobi and Danzo are similar. Tobi has bolts on the same arm that Danzo has covered up. They both share hair styles and have wrinkled faces. Danzo's right eye is covered by an eyepatch. Tobi's right eye is the eye that Tobi's mask reveals and is the same eye Madara has shown his Sharingan.

Trivia

 * Apparently, Madara and Konan are not on good terms with each other as he always questions Pain's abilities and she immediately scolds him for it despite him being their benefactor.
 * 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 have hilarious effect and as such, Tobi is depicted as a carefree child or a good natured character in many fan-made art and videos on Youtube while incorporating the phrase. Many have altered the phrase, after Tobi revealing that he's Madara, saying "Tobi is a Bad Boy".
 * Because the Raikage had requested for a summit of the five Kages, some speculate that Madara might appear at the summit. This is highly unlikely though, as Madara was a former Mizukage.
 * Despite Tobi and Madara being the same person in the third Databook they have different character profiles.
 * Madara has stated that Akatsuki didn't have the power to destroy Konoha. However, Pain was able to destroy most of the village, meaning that Madara might not know of Pain's true strength. (The village's destruction could be questioned as Pain hasn't completely destroyed Konoha since there were still many survivors. On the other hand Madara wanted revenge so the destruction of Konoha could be something he did not expected yet).
 * Since Madara was once the Mizukage, it is possible he was the Mizukage Zabuza Momochi tried to kill in his failed coup d'etat.
 * Madara and Orochimaru are extremely powerful ninja who share certain things in common: they both desired to be Hokage but were rejected, tried in failure to destroy Konoha, went on to become a leader of another village and an interest in Sasuke Uchiha.