Nagato (Japanese: 長門), known primarily under the alias of Pain (ペイン, Pein), is a fictional character in the manga and anime series Naruto created by Masashi Kishimoto, being a major antagonist in the series.

Nagato Uzumaki is the figurehead leader of the Akatsuki who wishes to capture the tailed beasts sealed into various people around the shinobi world. After acquiring and sealing most of the beasts within a Gedo statue, Nagato's advisor advises him to capture the Nine-Tailed Demon Fox sealed inside the series' main protagonist, Naruto Uzumaki (whom he turns out to be from the same clan: Uzumaki clan). Before leaving to capture Naruto, Nagato engages in a mortal battle with his former mentor, Jiraiya. His past as a war orphan, and his loss of his best friend are explored. Due to his traumatic experiences, which stemmed from human conflict, Nagato aims to create a new world, free from the chaos of war. Nagato also appears in the series' video games.

Nagato was conceived by Kishimoto as a villain, a victim of war, who would show Naruto the impact of world wars, something Kishimoto aimed to explore throughout the series. While Nagato does not fight in the story, he uses a group of corpses known as "The Six Paths of Pain" (ペイン六道, Pein Rikudō). All of them were given elaborate designs with multiple piercings across their bodies to reinforce the idea that despite his calm demeanor, Nagato is a dangerous person.

Critical response to Nagato's character has been generally positive, praising the chaos he brings to the story, including the murder of Jiraiya and the destruction of Konoha itself while chasing Naruto. His eventual fight against Naruto has been regarded as one of the best battles in the entire series.

Nagato originated from Masashi Kishimoto's desire to elaborate on the ending to the manga series Naruto. While the series was known for its fight scenes and tragedies, the main characters never experienced a war. Once the series began its "second part", simply referred to as Part II in the manga and Shippuden in the anime, Kishimoto felt the need to create a story arc that would emphasize the tragedy of wars, leading to the final arc which would include a war. The principal reason for this was a significant difference between the two main characters, Naruto Uzumaki who had no knowledge of wars, and Sasuke Uchiha who was a victim of one; his entire clan had been annihilated to avoid a potential civil war. As a result, Kishimoto created Nagato as a war victim who would kill Naruto's teacher, Jiraiya, and act as Naruto's nemesis so he would understand the tragedy that Sasuke had experienced. This led to the creation of the series' final arc, the Fourth Great Shinobi War, where Naruto engages in a bigger fight with the remaining member of the terrorist organization Akatsuki.

According to Kishimoto, Pain's story arc was the most difficult one to write; he felt this because the protagonist, Naruto, truly forgave his enemy. Instead of having the protagonist kill the enemy he hates as happens in other series, Kishimoto found the idea of the two characters interacting and settling their differences more challenging. This had a major impact on the writer, and he decided to have Naruto forgive Sasuke during their final fight in a similar manner as he interacted with Nagato. Retrospectively, Kishimoto believes Naruto took a darker tone with Nagato's introduction due to how his life indicated serious themes rarely present in shonen manga and thus often questioned himself what type of conclusion to this fight between the Akatsuki and the main character.

Regarding the bonds in the story, Kishimoto highlighted the importance of Jiraiya's death during his fight against Pain; this remark was made since, in his last moments, Jiraiya managed to discover the origin of Pain's multiple bodies and used his remaining forces to send a message to Naruto in which he explained how Pain can be defeated. As Nagato was Akatsuki's leader, Kishimoto aimed to give him a striking design showing an appealing look while simultaneously depicting him as a dangerous person. Since his alias is "Pain", he decided to add some piercings to his body—a metaphor for how he inflicts "pain upon himself". Notable among the few unused concept designs for him is a small sketch where Pain appears to wear a partial mask with a feather or horn-like accessories fitted to his forehead protector.

In the Japanese anime, Nagato's voice actor is Junpei Morita, while Yahiko/Deva(Literally meaning "God" in hindi)/Tendo Path is voiced by Kenyu Horiuchi; in the English dub, Nagato is voiced by Vic Mignogna, and Yahiko/Deva Path is voiced by Troy Baker (except for Ultimate Ninja Storm 4, where he is voiced by Matthew Mercer). While the other Paths shared the Deva Path's voice actors, the second Animal Path is voiced by Shiho Hisajima in Japanese and Stephanie Sheh in English. In regard to Nagato, Mignogna said "his story arc is amazing".