Askeladd (Japanese: アシェラッド, Hepburn: Asheraddo), whose full name is Lucius Artorius Castus (ルキウス・アルトリウス・カストゥス, Rukiusu Arutoriusu Kasutusu), is a fictional character from the manga Vinland Saga by Makoto Yukimura. Askeladd, the leader of a band of a hundred Vikings, bargains with Jomsviking commander Floki to kill the deserting warrior Thors. After a fierce swordfight, Thors defeats Askeladd but surrenders to save his son, the protagonist Thorfinn, and his villagers. After seeing his father's death, Thorfinn swears revenge against Askeladd, who recruits him into his group despite knowing his intentions.

The character was created by Yukimura to serve as a mentor to the inexperienced Thorfinn, despite both of them being enemies. Yukimura wrote him carefully until his last scene, which he calculated by writing his personality. In the end, the author was confused by how the character was written, as he felt the character became another father figure to Thorfinn, especially in his last moments. In Japanese, the character is voiced by Naoya Uchida, while David Wald and Kirk Thornton voice him in two separate English dubs.

Critical response to Askeladd was generally positive for being a striking villain and his relationship with Thorfinn. He was also listed as one of the best anime characters of 2019. Although Askeladd does not appear in the second arc, critics noticed the effect he had on Thorfinn, who tries to move through a different path than Askeladd's.

Askeladd shares the name of Askeladden, a Norwegian folk character known for his cleverness. His backstory is based on the early life of Olaf the Peacock, an Icelandic chieftain and major character of the Laxdæla saga. Manga author Makoto Yukimura commented that while most Vinland Saga characters were made to assist the protagonist Thorfinn, Askeladd was an exception. Because Thorfinn was inexperienced during the series' beginning, Askeladd was written to be a mentor figure who would lead him in the first story arc. He said that his relationship with Thorfinn was that of a father and son, respectively, as well as of enemies. The more the manga author wrote about these two characters, the more ambiguous it became, as he could not tell whether Askeladd was a good person or a hateful one. Askeladd had several contradictions, but he felt he was interesting like this. Yukimura early considered Askeladd a rudderless, disobedient habit that does its job and has some interesting behavior. Since the series is based on Vikings, Yukimura went to Norway and Scandinavia in 2003 to conduct research on Vikings. He was able to see the Oseberg Ship, which he says is the most beautiful ship he has ever seen, which Askeladd's forces use.

Several of Askeladd's lines are based on Yukimura's thoughts from his youth. When Askeladd makes fun of a slave and especially his owner for valuing themselves over money. Nevertheless, Yukimura ended up believing that society is slave of money itself. According to the author, Askeladd is a rather difficult character to understand but not completely bad when fully analyzed as he values others he would gladly follow like when trying to understand Canute. His friendship with Bjorn was not fully developed which was emphasized by their final interactions when the dying soldier asks Askeladd if they could have become friends at least. His relationship with Thorfinn was also seen close to that of a father and son despite their antagonism with the elder viewing himself as inferior during his last moments and urging Thorfinn to take a better life and follow Thor's values about becoming a true warrior rather than attack Canute.

Despite Askeladd's ruthless and violent character, Yukimura felt that he was still appealing. The author believes that Askeladd tends to escape from battles he cannot win and thus was out of character when acting desperate in front of Torgrim. His ideal of having more power is the greatest turning point for him. This led to the idea of Askeladd joining forces with Prince Canute to take over Sweyn's forces while manipulating the future King. Askeladd's last yell towards Thorfinn, when he kills Sweyn and pretends to be insane, was written at the last moment. Yukimura felt that Askeladd would show more humanity towards Thorfinn in his last moments when writing the chapter. Yukimura sees Askeladd as Thorfinn's second father, even though his personality is cold and inspires him to become violent. These father-and-son relationships are common in Vinland Saga, and they were all written from Yukimura's experience as a father.

For the anime adaptation, Studio Wit said there was a strong sense of camaraderie toward an individual, Askeladd, that brought the Vikings together. They portrayed Askeladd as being able to take charge because others viewed him as powerful. They were also careful not to depict the supporting characters as overly dependent on their leader, as that would diminish their charm. The anime also added new scenes about how Thorfinn turned into one of Askeladd's soldiers rather than just making a time-skip, which the manga artist appreciated. The director claimed that for these anime-original scenes, they also tried to keep Askeladd in character. He further said that the story about Askeladd's forces was entertaining to see.

Yukimura claimed that due to the Vikings being famous for committing violent deeds, he decided to write a story where Askeladd's group murders an innocent Christian family in order to generate a major shock within the readers. "In that world, Christians work hard with fear every day to get to heaven someday, but when they see Askeladd destroy their common sense in such a way, Anne feels guilty for feeling a certain admiration for it." Askeladd's deeds were also meant to shock the only surviving woman, who wonders whether the God she prays to is real. Askeladd's violence is also motivated by survival, and thus he kills people for the sake of it. This was also done because Yukimura wanted the character to be seen more as a villain.