Rudeus Greyrat (Japanese: ルーデウス・グレイラット, Hepburn: Rūdeusu Gureiratto)[a] is the main protagonist of Rifujin na Magonote's novel series Mushoku Tensei.

Awakening as a newborn baby, he realizes that he's been reincarnated in a world of sword and sorcery and resolves to live his second life to the fullest as Rudeus Greyrat.

Due to inherited affinity and early training, in addition to his mother's influence, Rudeus becomes highly skilled at magic, and sets out to enjoy life and overcome his past.

Rifujin na Magonote said he came up with Rudeus' story by the premise of what he would do with his life if he was in another world; The idea of having a better childhood was the chosen for protagonist.

[11] Producer Nobuhiro Osawa expressed doubts about whether or not the team was sure about including more sidestories from the original series that helped in developing more Rudeus.

The producer noted that while Rudeus comes across as a crude person, he had a major changed after properly interacting with his father, to the point it became his favorite part so far.

[14] The reason the anime staff cast Tomokazu Sugita as the man in Rudy's previous life was because when the director read the original story, he thought it was "impossible for him [Rudeus] to be [portrayed by] anyone else".

[17] In the scene where Rudeus and Paul quarrel in episode 3, Uchiyama was able to know that there was a conflict from the perspective of the parents, but it is because the backbone and human drama of each of those characters are drawn very carefully.

In November 2021, Morris claimed she grew fond of Rudeus due to all the hidden depths he has, which leaves his traumatic past as a mystery.

During his childhood, he becomes a student of demon magician Roxy Migurdia, a friend to demihuman Sylphiette, and a magic teacher to noble heiress Eris Boreas Greyrat.

The Mushoku Tensei series is divided in several story arcs that follow Rudeus' coming-of-age from an infant surpassing his Hikikomori fears while learning magic from Roxy.

Rudeus starts a journey across the world as a major magical catastrophe destroys his nation, teleporting and stranding hundreds of thousands of people far from home.

He meets a strange Human figure who often guides him In the last chapter of the "Boyhood arc", Rudeus becomes intimate with Eris but she abandons him shortly without word, making him believe he was rejected.

A few months later, Sylphiette gets pregnant with their child, but Rudeus receives a letter from his father Paul, asking for his help to rescue his mother Zenith, who is trapped inside a labyrinth in the distant Bengaritt Continent.

Rudeus joins Paul and their party to fight and defeat a hydra in the deepest part of the labyrinth to rescue Zenith, but he loses his left hand and his father is killed in the occasion.

[26] The initial response to Rudeus was generally negative, with Anime Feminist calling out his lust for women with the mention of lolicon in the novel, making him come across as disgusting.

His first interactions with Roxy were also called out for how Rudeus takes advantage of his young age to accidentally spy on her while suggesting that she could be his future wife due to her antisocial personality.

[27] Anime News Network found Rudeus hard to sympathize, as in early chapters he barely develops connections, to the point he always refers to his parents by their names.

[29] HITC found the anime properly followed the novel's narrative, most importantly Rudeus' coming-of-age story, which appealed to the audience.

[36] The Fandom Post also claimed Rudeus has one of the biggest character developments in anime history as he continuously tries to better himself while dealing with his past life's regrets.

[37] Re:Zero − Starting Life in Another World novelist Tappei Nagatsuki said that one of the strongest points of Mushoku Tensei was the handling of Rudeus who is noted to suffer similarly to the main character from the visual novel Clannad.

[38] Upon the reveal of Rudeus' teenage persona, Yahoo praised the design due to how striking it was and looked forward to his role in the second season.

[43] Irfan Ghani Muhammad from Universitas Kiai Haji Achmad Siddiq Jember [id] noticed Mushoku Tensei often tests Rudeus' morality from different point of views.

This often leads to the main character thinking from another point of view to fill peaceful solutions to his problems with others, which expands on the idea of Rudeus becoming more active and mature than in his past life.

Once again, Rudeus thinks about his personal problems from his previous life and searches for the most adequate solution to solve his dilemma with Paul and form a more genuine bond with his father, staying true to his decision having less regrets.

[48] Rifujin's comment attracted controversial and negative response in media, which led him to clarifying that he does not condone slavery and neither does his character as "the original story is written with a kind of mild setting where it is accepted that".