Mushoku Tensei: Jobless Reincarnation (Japanese: 無職転生 〜異世界行ったら本気だす〜, Hepburn: Mushoku Tensei: Isekai Ittara Honki Dasu, lit. "Jobless Reincarnation: Giving His Best When Transferred to Another World") is a Japanese light novel series by Rifujin na Magonote[a] and illustrated by Shirotaka. The series is about a jobless and hopeless man who dies after having a sad and withdrawn life and reincarnates in a fantasy world while keeping his memories, determined to enjoy his new life without regrets under the name Rudeus Greyrat.

Originally published on the internet web novel website Shōsetsuka ni Narō in November 2012, a year later it was announced the series would receive a print release under Media Factory's MF Books imprint with illustrations done by a Pixiv user called Shirotaka. A manga adaptation by Yuka Fujikawa began serialization in the June 2014 issue of Monthly Comic Flapper while three spin-offs were also released. Seven Seas Entertainment licensed the tankōbon volumes of the manga for localization in North America. The company also has licensed the original light novels. An anime television series adaptation produced by Studio Bind aired from January to December 2021. A second season premiered in July 2023.

Mushoku Tensei: Jobless Reincarnation has become a success, with its web novel published from Syosetu's rankings has made cumulative appearances as the most popular work on the website, and later expands into a franchise began in 2014. By June 2023, the franchise had over 13 million copies in circulation. Although early volumes of the light novels were the subject of controversy due to sexual themes leading to censorship and complaints, the latter chapters of the series were subject of praise for the development and handling of Rudeus' growth.