Kovu is stated to be the youngest son of Zira, a follower of Scar; his two older siblings are Nuka and Vitani. He was apparently born at some point during Scar's reign, as Scar hand-picked him to be his successor. As a result, he was referred to by the Outsiders as the Chosen One. However, Scar merely adopted him, and Kovu is of no relation to Scar. His chosen path was put to a halt after Simba took back the throne from Scar and exiled the Outsiders. As a result of Scar's death, Kovu was expected to one day avenge Scar by killing Simba and usurping the throne. As a cub, he was put through harsh training by Zira to prepare him for this task.
Kovu is aggressive and crude, even as a cub. Upon first meeting Kiara, his first reaction is to snarl a challenge, and the only game he appears to understand is play-fighting. His violent tendencies are reinforced by a knack for taking care of himself, as he is physically fit and an able hunter, two features that make way for his more arrogant and cocky side. Even as a cub, Kovu strives to please and takes no shame in showing off to the more innocent Kiara. However, when faced by his mother, Kovu is submissive and prone to showing his softer side, exposing a desire to befriend and treat kindly the new cub he has just met. After meeting Kiara again as an adolescent, Kovu begins to cave to his inner good, proving himself to enjoy laughter and good times.
Kovu is noted by many to bear a strong resemblance to Scar.
His fur is auburn, and his muzzle, paws and underbelly are all creamy brown in color. He sports a dark brown head tuft and also sports tufts of fur on his elbow joints that match the color of his head tuft and tail tip. His dark eye shades mirror those of his siblings, but his emerald green eyes match no member of his family's.
As an adolescent, Kovu's mane is colored a very rich dark brown and matches the dark shades of his elbow tufts and tail tip. He later gets a scar across his left eye that is inflicted by Zira.
One day, Kovu escaped from his brother Nuka, who was supposed to be watching him. While wandering about, he met Kiara, Simba's daughter, who had wandered in the Outlands. The two cubs became friends after an incident with crocodiles, but they were quickly separated by their feuding parents. Back home, Zira angrily scolds Kovu for trying to befriend an enemy but then realizes she may be able to use the friendship to allow Kovu to get close to Simba and kill him. She then praises Kovu for his brilliance, stating that he has the "same conniving mind" that Scar had.
When Kovu has grown into an adolescent, Zira sends him to the Pride Lands to initiate her plan. As part of the plan, he rescues Kiara from a wildfire that has been set by Nuka and his sister Vitani. After rescuing Kiara, he asks Simba to allow him to join the Pride Landers. Though Simba rejects him initially, it is pointed out that by law he owes Kovu a debt for saving Kiara. As repayment, Kovu is allowed to return to the Pride Lands; however, Simba still doesn't trust him. Simba chooses to reserve his final judgment until he can learn about Kovu's character and forces Kovu to sleep outside the den away from the pride. Kovu appears briefly in Simba's nightmare, where Scar turns into him and throws Simba off a cliff into the stampede (similar to how Scar killed Mufasa in the first movie).
During his time at Pride Rock, it becomes apparent that Kovu has never had any real fun before. When Kiara chooses to chase birds alongside Timon and Pumbaa for the fun of it, Kovu believes it to be training. Kiara teaches him to loosen up and enjoy himself. Over time, he grows fond of Kiara and begins to fall in love with her, a feeling which is encouraged by a meeting with Rafiki, and begins to question his role in Zira's plot. Later, Simba finally warms up to Kovu and thanks him for saving his daughter's life the other day, and invites him in the den with the pride. The next morning, Kovu resolves to reveal Zira's plot to Kiara and that he doesn't want to be a part of it anymore because he loves her, but is prevented from doing so when Simba takes him alone to talk. After hearing Simba's retelling of Scar's story, he realizes how just how wrong his mother has been in her opinion of Scar. However, the two are ambushed by Zira and the Outsiders, who had been spying on Kovu and realized he was having second thoughts. Zira frames Kovu, claiming that the ambush was part of the plan. Kovu denies it, but Simba believes it anyway and quickly distrusts him. Kovu attempts to defend Simba but is knocked unconscious by Vitani.
After Simba manages to escape the Outsiders, Kovu rushes back to the Outsiders to see about Nuka, who had been trapped under falling logs while trying to attack Simba. Nuka dies as a result of his wounds, and Zira angrily blames Kovu for Nuka's death, scarring him across one eye, reminiscent of Scar's appearance. In response, Kovu stands up to his mother for the first time, rejects Scar, and runs off. Back at Pride Rock, Simba believes that Kovu was behind the ambush, and exiles the rogue lion from the Pride Lands, ignoring Kiara's protests. As Kovu flees, he was being watched by Rafiki from a distance who sighs very sadly while realizing that Simba has completely defied his father's goals and broken the Circle of Life. However, Kovu later reunites with Kiara, who had run away from Pride Rock to find him. The two briefly discuss running away to form their own pride, but Kiara convinces Kovu that they need to return to try and unite their prides.
Kovu and Kiara return to find the Pride Landers and the Outsiders engaged in a bitter war, with Simba and Zira preparing to fight one on one. Kovu and Kiara manage to separate them, and Kovu publicly announces his intention to not let Zira harm either Kiara or Simba. As a result of his and Kiara's actions, Vitani leaves Zira's side, with the other Outsiders following her after Zira threatens to kill Vitani. When Zira attempts to attack Simba, Kovu looks on as Kiara fights her in an attempt to save her father. He sighs sadly as he sees his mother fall to her death. Simba apologizes to Kovu for his mistake and allows him to return to the Pride Lands, where he is united in marriage with Kiara by Rafiki.
Kovu, along with Nuka, Vitani, Zira and their pride return in the Disney Junior series The Lion Guard episode "Lions of the Outlands", which takes place sometime after Kovu's first meeting with Kiara. He is very hopeful when Kion says he could get them back in the Pride Lands due to his desire to see Kiara again, something Kion had no knowledge of until then.
When Zira and her minions are blown out of the watering hole, (which they had taken from Jasiri's clan) by Kion's Roar of the Elders, Kovu manages to avoid being blasted away. When Kion starts to approach him, Kovu runs after his mother, siblings and pride.
- "Kovu" means "scar" in Swahili.
- Sora's lion form in Kingdom Hearts resembles Kovu.
- Kovu was originally going to be Scar's biological son, however, Micheal Eisner decided that Kovu shouldn't be related to Scar, as it would cause incest between him and Kiara as "first cousins". His mane was also black during early development stages.
- In the documentary Proud of Simba's Pride, Kovu is described as a "teenage killer". So that would mean that his adolescent self is the equivalent of an 18- and 19-year old.
- In The Lion Guard, he always seems to be the least aggressive Outsider which means that his intensive training has not yet made him more aggressive. However, he was able to stand up to Nuka and stick up for Jasiri when Nuka prepared to attack her, implying that his intensive training has at least made him, to some degree, assertive.
- In The Lion Guard, Kovu's voice appears to have deepened, implying that he has aged since his first meeting with Kiara. Also, Kion expresses shock when learning of Kovu's friendship with his older sister. This could mean that Kion was either not born yet or was an infant when Kiara and Kovu met.