Kakashi is the son of Sakumo Hatake, also known as the "Konoha's White Fang." Not much is known of his mother other than that she died when he was young. Kakashi has been known since a young age as an extremely gifted prodigy, regarded by many as the best of his generation. He had received top marks and had shown an innate aptitude for the ninja arts while in the Academy. This permitted him to graduate from it in a single year at the top of his class at the age of five, and then becoming a chunin a year later, facing and defeating Might Guy during the third stage of the Chunin Exams.
Despite his own success, his father fell into disgrace after choosing to save his comrades rather than complete an important mission, causing Konoha to suffer in the war effort. Dishonoured, Sakumo took his own life after a deep depression and a drop in his skills, which caused Kakashi to lead his life strictly by the ninja code.
Kakashi was teamed with Obito Uchiha and Rin under the leadership of Minato Namikaze. At the age of 13, soon after becoming a jonin, Kakashi was assigned to lead Obito and Rin on a mission that would benefit Konoha in the ongoing Third Shinobi World War. They were to destroy Kannabi Bridge, which was being used by Iwagakure forces to move into Kusagakure. This would also be Konoha's first huge offensive move in the war. On their way to the bridge, Rin was kidnapped by two Iwagakure ninja named Kakko and Taiseki. Obito immediately suggested that they rescue her, but Kakashi disagreed on the basis that they needed to complete their mission, opting not to make the same mistake his father did.
Obito would not hear of it and stubbornly left to save Rin, but not before mentioning that he believed Kakashi's father, the White Fang, was a true hero. Shortly after parting ways, Kakashi reflected on Obito's words and Rin's prior kindness. He realised that his father was not wrong after all, which prompted him to join Obito in the rescue effort. Kakashi arrived in time to save Obito from Taiseki, using his father's blade to combat him. Despite the two-to-one disadvantage, the more experienced Taiseki was able to attack and damage Kakashi's left eye, who took the blow that was intended for Obito, giving him a permanent scar and blinding the eye.
Obito's will to protect his comrades would cause his Sharingan to awaken, and he uses it to kill Taiseki. Finding Rin and defeating Kakko with Obito's help, Kakashi freed Rin before their opponent uses a crushing earth technique to trap them in a cave-in. While trying to escape, Kakashi was hit by a rock which he didn't notice because of his bandaged eye causing him to fall. Obito pushed Kakashi out of the path of a falling boulder, causing himself to be crushed beneath it instead. Knowing he would die, Obito instructed Rin to implant his left Sharingan into Kakashi's damaged eye. Rin complied, and as soon as the surgery was completed Kakashi used the Sharingan and his Chidori to kill Kakko. He then returned to Obito to see if there was anything he could do for him, but was forced alongside Rin to leave him. With the help of Minato, they ultimately completed their mission, allowing them to mourn Obito's supposed death.
Some time after the events at Kannabi Bridge, the pair were apparently sent out on a mission where they were ambushed by jonin and ANBU-level Kirigakure shinobi. The events of this encounter culminated in a tearful Kakashi running Rin through her chest with his Chidori.
Soon after the end of the war, when the Nine-Tails attacked Konohagakure, Kakashi and the rest of his peers were barred from participating in the defence of the village by Kurenai Yuhi's father and other older shinobi.
Over the years, Kakashi became well-known among all the Five Great Shinobi Countries for the extensive use of his Sharingan, gaining him a reputation as "the man who has copied over a thousand techniques", hence his nickname. Kakashi eventually joined the Konoha ANBU, and also served as a mentor to Tenzo.
Kakashi with his ninken during his ANBU days.
He later left for unknown reasons, but maintained strong connections with the ANBU. Kakashi eventually became a team leader, and tested many genin. As the Third Hokage told Iruka, Kakashi had never passed any of them due to their inability to live up to his expectations of working as a team.
In the anime, he once had a mission where one of his team-mates, Iruka Umino, was injured, paving the way for the latter to become an instructor at the Academy. When Iruka was having doubts at being assigned to be the home room teacher of Naruto Uzumaki, Kakashi served to remind him of his real reasons for wanting the post in the first place.
Although later earning status as a jonin-sensei, Kakashi developed a reputation throughout the academy for having exceedingly high standards on who he would train, and failing every potential genin team that took the survival training exam he proctored. When he was given the next potential Team 7 — which consisted of Naruto Uzumaki, Sasuke Uchiha, and Sakura Haruno — he gave them a bell test, requiring the three of them to obtain at least one bell that he keeps on his waist. With only two bells available and three genin present, his students believed the test to be a competition against each other and so they worked independently in the attempt to take a bell.
Each of the young ninja try their own methods to getting a bell, only for Kakashi to easily defeat them. After Team 7 failed their test, Kakashi was quick to express how displeased he was with their performance. After belittling each of their performances, he revealed the true goal of this test: teamwork. After explaining the importance of teamwork and seeing how ashamed they were at their performance, Kakashi decided to give Team 7 one more chance to act as a team, and let them take a break for lunch. However, Naruto, having earlier tried to steal their lunches, was forbidden to eat. Deciding that they would need Naruto in peak condition if they were to work together, Sasuke and Sakura gave him food anyway. Kakashi witnessed this act and immediately confronted them, feigning anger that they disobeyed him, before passing them. The newly formed team explained that they needed to work as a team first before anything else. He then congratulated them on being the first team to pass under him after revealing the true objective of the test: teamwork and loyalty to your team-mates.
It was later revealed that Kakashi was chosen specifically to be the leader of Team 7 because of Naruto and Sasuke. Kakashi's duty in addition to training the team was also to keep the Nine-Tailed Demon Fox in Naruto contained, and to keep Sasuke from walking down a dark path, since they had similar traits that would allow Kakashi to better understand him.
After completing a number of easy D-rank missions, Team 7, at Naruto's insistence, was assigned a somewhat more difficult C-rank task of escorting the bridge-builder Tazuna to the Land of Waves. They were attacked en route by the Demon Brothers. After Kakashi easily defeated them, he realised that there was more to the mission than a simple escort, and convinced Tazuna to tell them the truth, that the Land of Waves was under the tyranny of Gato. Tazuna hoped to build a bridge that would free the country, and had thus garnered Gato's assassination attempts. Even though the mission was far more dangerous than what they had been initially assigned (A-rank, B-rank jonin difficulty), Team 7 agreed to act as his bodyguard until the bridge was complete.
Upon arriving in the Land of Waves, Team 7 was attacked by Zabuza Momochi, another of Gato's hired assassins. Zabuza's superior experience with water-based techniques, combined with Kakashi's focus on protecting his team-mates, allowed him to catch Kakashi off guard, resulting in Zabuza trapping Kakashi with a water prison. Kakashi pleaded with his students to flee with Tazuna, but they instead chose to work together, and managed to free him. Using his Sharingan, Kakashi was able to turn the tide against Zabuza. Before Kakashi could land a killing blow, a boy named Haku stepped in, and appeared to kill Zabuza first. He then took Zabuza's body away, claiming that he was a Kirigakure hunter-nin and would dispose of it, after which Kakashi collapsed from exhaustion due to overuse of his Sharingan.
Realising that Haku might have faked Zabuza's death to save him, Kakashi trained Team 7 to gain better chakra control while recuperating. In a week, they had mastered the training, and thus resumed their bodyguard duty. At the bridge they were confronted by Zabuza and Haku, confirming Kakashi's suspicions. While Haku engaged Naruto and Sasuke, Kakashi fought Zabuza.
Having learned from his defeat, Zabuza relied on sneak attacks during the battle through his Hiding in Mist Technique to keep him from falling prey to Kakashi's Sharingan. In response, Kakashi summoned his ninken underground to locate and pin down Zabuza, making him an easy target for his Lightning Cutter. Before he could kill Zabuza, Kakashi was once again interrupted by Haku, who used himself as a human shield and took the blow intended for Zabuza, thus being killed in the process.
Still determined to win, Zabuza relentlessly attacked Kakashi but the battle turned completely in Kakashi's favour, as he easily outmanoeuvred Zabuza. Gato and the rest of his henchmen later showed up to have Zabuza disposed of as a result of his failure, only for Zabuza to kill Gato. While Kakashi witnessed the event, Gato's henchmen in turn killed Zabuza. In response, Kakashi used his Multiple Shadow Clone Technique to scare the thugs away. As Zabuza died, he asked Kakashi to bring his body beside Haku's before he passed away. Kakashi buried them alongside each other before returning to Konoha with Team 7.
Feeling his students were ready, Kakashi entered Team 7 in the Chunin Exams, despite some initial disapproval from other elite ninja. After Sasuke was branded with the Cursed Seal of Heaven by Orochimaru during the exam's second phase, Kakashi took it upon himself to deal with the cursed seal. Unable to remove it, he instead used the Evil Sealing Method to try and prevent its usage. Following the preliminary matches, Kakashi decided to personally train Sasuke for a month after realising how much Orochimaru desired Sasuke from his subordinate Kabuto Yakushi attempting to abduct him. Kakashi tried to reinforce Sasuke’s self-worth and value for his friends by teaching him how to use Chidori as a deterrent against the cursed seal. As the training also involved taijutsu training copied from Rock Lee to better condition Sasuke's body for the Chidori, Kakashi runs late in delivering Sasuke to his final round match. When Sunagakure and Otogakure's invasion of Konoha began during Sasuke's match, Kakashi released a genjutsu along with Might Guy and Sakura, and helped repel the invaders along with Guy. They ended up having several contests to see who could defeat the most Suna and Oto-nin, although Guy usually won. When he noticed that Sasuke was going after Gaara, Kakashi sent Naruto, Sakura, Shikamaru Nara, and Pakkun to stop him and bring him back. After defeating several Suna and Oto-nin, he is briefly seen with Guy, Aoba and Kurenai. After the failed Invasion, he attends the Third Hokage's funeral, mourning his loss, he listens to Iruka's words at the funeral and thinks how sad it would be if the Third had died for nothing.
Shortly after the invasion was prevented, Itachi Uchiha, Sasuke's older brother, and Kisame Hoshigaki of Akatsuki infiltrated the village. Asuma Sarutobi and Kurenai Yuhi tried to apprehend the two, but they were almost killed, making Kakashi intervene. Although Kakashi was able to hold his own against Itachi for a short while, Kakashi fell victim to Itachi's Tsukuyomi. Severely weakened by the technique, Kakashi confirmed that Itachi and Kisame were after Naruto and the Nine-Tails before collapsing. With Kakashi's knowledge on them, Itachi ordered Kisame to kidnap Kakashi. Luckily, Guy arrived just in time to drive the Akatsuki members off.
Kakashi was left in a coma after what happened, and was not revived until Tsunade returned to the village. Immediately after recovering, he was sent on a new mission.
Before setting out on his mission, Kakashi stops a battle between Naruto and Sasuke. Learning that in his absence, Sasuke had begun reverting to his obsession for power and revenge. Kakashi lectures Sasuke about misusing the Chidori, pointing out that it was designed to protect friends, not attack them. He encourages Sasuke to place greater importance on friendships than on revenge, then leaves to let his words sink in, unaware that Sasuke was given little time to embrace those words thanks to Orochimaru’s Sound Four.
When Kakashi returned from his mission, he found out that Sasuke had defected to Orochimaru, and that a squad of genin, led by Shikamaru, was all that had been sent out to retrieve him. Ignoring the fact that he had a new mission, Kakashi rushed out to track down Sasuke and the retrieval team. Using his ninken, Kakashi was able to locate a defeated Naruto, with Sasuke having already left. Unable to pursue Sasuke because of a fresh rainfall and due to Naruto's current condition, Kakashi took Naruto back to the village to recover, saddened that he failed to help his students.
Kakashi continued to be sent on missions during the anime's filler arcs, leaving him with very few appearances. He returned from a mission in time to recapture some of the prisoners that had escaped from prison when Mizuki led a breakout. He was later sent to assist with the Cursed Warrior incident in the Land of Birds. While not officially his mission and arriving much later, Kakashi realised the situation wasn't as it seemed, and ultimately took command of the team, thereby deciding to investigate. This led to Kakashi's fight with Hoki's minions, Nagare and Hokushin, whom he defeated with relative ease.
In the Ultimate Weapon Arc, Kakashi was sent to spy on the Takumi Village when rumours of an uprising reached Konoha. There, he discovered the entire village abandoned, and the corpses missing. He later showed up towards the end of the arc, where he was sent as part of reinforcements, along with Jiraiya, to aid Naruto and the rest of the genin in helping Sunagakure, only to discover that Naruto's team had already successfully completed their mission. At the conclusion of Part I, Naruto and Sakura began training under Jiraiya and Tsunade respectively, leaving Kakashi free to train himself.
With Team 7 effectively dissolved, Kakashi spent the two and half years further enhancing and refining his abilities to prepare for the inevitable battle with Akatsuki. After Naruto's return to the village, Kakashi was given, by Naruto, the newest edition to the Icha-Icha series. Later, Kakashi had Naruto and Sakura take another bell test, with the real objective being to actually capture the bells, to see how much they have improved. When they were unable to get close enough to Kakashi to each take a bell, Naruto and Sakura resorted to trying to spoil the plot of the most recent Icha-Icha novel, throwing Kakashi off guard and allowing them to take the bells.
When word reached Konoha that Gaara had been kidnapped by Akatsuki, Team Kakashi was sent to rescue Gaara. Upon arrival in Sunagakure, they are teamed with Chiyo before following Akatsuki's trail. Along the way, they encountered Itachi. Kakashi was able to fight on even grounds in this battle, but noted that Itachi's performance wasn't what it was the last time they met. With a well-timed manoeuvre, Kakashi was able to trick and restrain Itachi, giving Naruto the opening needed to finish the fight with his Big Ball Rasengan. Afterwards, they discovered that the Itachi was only a lookalike. They then met up with Team Guy, which was sent as back-up to Team Kakashi, outside an Akatsuki lair. Because there is a barrier over the entrance, Team Guy went to take down the barrier. This allowed Team Kakashi to infiltrate the lair, where they found Sasori, Deidara and Gaara