One Piece features various enigmatic elements that are the subject of intense debate and discussion among fans, and one of the most popular among these is Imu’s immortality. As the ruler of the World Government and a primary antagonist in the series, Imu is a mysterious figure whose appearance, gender, and age are unknown.
Apart from a few brief appearances, most assumptions about them are drawn from subtle hints provided throughout the story. Using these, it is safe to presume that Imu does have some form of immortality. Ever since their first appearance, Imu has been a figure who inspires fear in all those around them.
They overturned the power hierarchy in the One Piece world, sitting on the Empty Throne and commanding the Gorosei. Since then, Imu has consistently shown that they are the most formidable person in the series. They killed Cobra, harmed Sabo, destroyed the Lulusia Kingdom, and are currently causing devastation across Elbaph.

At the same time, a key character trait of Imu is their hatred of Joy Boy and abhorrence of the Void Century. They despise Nefertari D. Lili, who existed 800 years in the past, for having spread the Poneglyphs around the world. Imu also seems to harbor a deep resentment toward the Will of D.
While the reason for their animosity has never been revealed, it is too intense to simply be a grudge passed down the family, especially when the Void Century had taken place nearly a millennium ago. During a meeting between the Revolutionaries, Emporio Ivankov gave insight into Imu, stating that they may have existed during the years of the Ancient Kingdom.
Common knowledge had indicated that Saint Nerona Imu was part of the twenty founding families of the World Government, and Imu, by extension, would be their descendant. However, Ivankov suspected that Imu may be the person themself. Imu’s possession of an Ancient Weapon and close connection to different elements of the Void Century would act as a testament to this theory.
Additionally, both the Five Elders and the God’s Knights are also near-immortal, suffering little damage against fatal attacks. The only one who seems to control their lives is Imu, who killed Saint Saturn due to his failure at Egghead. It would be highly unusual for Imu to not be immortal if they could manipulate the fates of other supreme beings.
How is Imu immortal in One Piece?
There are currently two major possibilities on how Imu became immortal in One Piece. Up till recently, most believed it was the result of the Ope Ope no Mi’s Immortality Operation, which would allow the user to grant another person immortality at the cost of their own life. Doflamingo sought to obtain this from Law. Imu may have received the effects of this operation sometime during the Void Century.
However, recent chapters of the Elbaph Arc revealed another likelihood - Imu is a devil. After taking over Gunko’s body in the land of the giants, Imu’s appearance was much like the devils mentioned in folklore. Additionally, through their magic, they could turn giants like Dorry and Brogy into evil undying demons by submerging them into the Abyss.
Since all the God’s Knights transport themselves using the Abyss, they seem to be capable of doing so only because of Imu. It has not been revealed whether Imu’s powers are from a Devil Fruit. However, given how rich One Piece’s world is and its many unexplored elements, it would not be unusual for a race of devils and demons to also exist.
Therefore, based on the various pieces of evidence placed across One Piece's narrative, there is little doubt that the dangerous antagonist Imu is immortal. This significantly heightens the stakes, forcing the Straw Hats to unlock a new level of power in order to stand up for their ideals.