Subaru Natsuki is a NEET who is suddenly summoned to a fantasy-like world. Just after arriving, he is killed while trying to help a young half-elf he befriends, Emilia, who is a candidate to become the next ruler of the Kingdom of Lugunica, only to revive some hours in the past. After dying a few times, Subaru realizes that he has the power to turn back time after his death. After successfully helping Emilia, Subaru starts living in one of the Mansions of Roswaal L. Mathers as a butler. Out of gratitude and affection for Emilia, Subaru makes use of his newfound ability to protect her and help on her ambition to be successfully appointed as the next queen, also providing assistance to other friends he makes along the way, while suffering due to the pain inflicted on him every time he dies, and carrying along the memories of everything that happened before his power activates, which is forgotten by everybody except for him.

In the late 2000s, the light novel series The Familiar of Zero (Zero no Tsukaima) spawned a number of fan fiction on the website Shōsetsuka ni Narō ("Let's Become Novelists"), also known as Narō. Tappei Nagatsuki initially began writing The Familiar of Zero fan fiction on Narō, before building on its isekai ("other world") concept to write his own original web novel series on Narō, called Re:Zero, which began serialization in 2012.

The series' editor at MF Bunko J, Masahito Ikemoto, first became aware of the web novel in April 2013, when it began to appear on his Twitter feed. He was immediately impressed by the series' use of Return by Death, and how it was a "depressing, yet surprising, twist on the fantasy genre", and began working with Nagatsuki to adapt the series into a light novel. Most light novels are around 250 pages in length, but Nagatsuki submitted a manuscript of more than 1,000 pages for the first novel, forcing Ikemoto to edit it heavily. While Nagatsuki wanted to engage in worldbuilding early on, Ikemoto felt that it was more necessary to make the readers feel engaged with the characters. He ended up rearranging the story so that parts focusing on the world and its lore were pushed back to the third arc of the series.

Prior to his involvement in Re:Zero, illustrator Shin'ichirō Ōtsuka worked on video games, which led him to draw the backgrounds first when illustrating the series. After reading the web novel, he submitted a number of character designs for the major characters to Ikemoto. Subaru's initial design made him look like a delinquent, with Otsuka later describing it as "not the face of a boy in his teens", leading Ikemoto to request that the character be "more friendly and less fierce" so that the audience could empathize with him during emotional scenes. Originally, Emilia's character design appeared extremely plain, so a number of features were added to make her more interesting. Ikemoto specified that she must fit the "archetypal heroine" mold. Ram and Rem also underwent significant changes from the first draft: their original designs lacked the characteristic hair parts, and their maid uniforms were longer and more "traditional".
The possibility of an anime adaptation came up early in the development of the series; Shō Tanaka, a producer at Kadokawa, asked Ikemoto about properties which might lend themselves to being animated, and Ikemoto recommended that Tanaka read Nagatsuki's web novels. Despite an initial miscommunication which led to Ikemoto believing that Tanaka wasn't interested, talks of adapting the series began soon after the web novels began the transition to print.

As part of talks for the potential anime adaptation, Ikemoto and Tanaka spoke to Tsunaki Yoshikawa, an animation producer at studio White Fox, about the possibility of his studio animating t…

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According to Japanese light novel news website LN News, the series had 1 million copies in print by June 2016; over 2 million by September of the same year; and over 3.1 million by May 2017. It had over 11 million copies in circulation by January 2022. The overall series (light novel and manga adaptations volumes) had over 13 million copies in circulation by March 2023 (including digital versions). The light novel series was the tenth best-selling light novel series in Japan between November 2015 and May 2016, selling 263,357 copies. During that period, the first and second volumes were the 35th and 48th best-selling light novel volumes, selling 49,194 and 41,617 copies, respectively. The series was the fourth best-selling series in 2016, selling 1,007,381 copies between November 2015 and November 2016. Its first three volumes were the fourteenth, 21st, and 30th best selling volumes of the year, selling 155,363, 127,970, and 110,574 copies, respectively. In 2017, the series was the third best-selling series, with 925,671 copies sold. Its first, tenth, eleventh, and twelfth volumes respectively ranked nineteenth (60,135 copies), 25th (56,001 copies), seventh (101,480 copies), and twelfth (79,431 copies) in the period between November 2016 and May 2017. In 2019, the series sold 550,202 copies.

The series was the 21st best selling anime series on home video during 2016, selling approximately 68,791 Blu-ray and DVD sets. The OVA, "Memory Snow", released in 2018, sold a total of 10,429 Blu-ray and DVD copies.

Theron Martin of Anime News Network reviewed the first book, praising it for being a somewhat fresher take on the "transported to another world" concept, but leveled criticism at it for bumpy and awkwardly timed dialogue and a tendency for redundancy.

The series ranked first in a poll of 820 people conducted by the Japanese website Anime! Anime!, to determine the best show of spring 2016. Andy Hanley from UK Anime Network considered the anime adaptation as one of 2016's best series.

The Managing Editor from Anime Now!, Richard Eisenbeis lists the anime as one of his top picks from 2016 for its "culturally complex" world and characters that have "their own plans, faults, and motivations." He praised Subaru as the "most complex character of the year" due to provoking the audience to "cheer him and despise him" in a world that portrayed him as the "least special person in it."

The series took second place in the 2015–2016 Newtype Anime Awards. Additionally, director Masaharu Watanabe took first place, as did Subaru, Rem, and Puck (in the best male, female, and mascot character categories, respectively). Masahiro Yokotani's screenplay took second place, while the series' character designs (by Shin'ichirō Ōtsuka and Kyuta Sakai) took third place. The series' soundtrack and second opening theme both took fourth place in their categories. The light novels and the anime both took first place in their respective categories in the 2017 Sugoi Japan Awards.

In a survey of (primarily female) Otamart users, the series was ranked second on a list of the most successful anime/manga/light novel franchises of 2016. R…

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