Tensei shitara Slime Datta Ken (Japanese: 転生したらスライムだった件 Hepburn: Tensei Shitara Suraimu Datta Ken) is a Japanese fantasy light novel series written by Fuse, and illustrated by Mitz Vah. It was serialized online between 2013 and 2016 on the user-generated novel publishing website Shōsetsuka ni Narō. It was acquired by Micro Magazine, who published the first light novel volume in 2014. Fifteen volumes have been released as of September 2019. The light novel has been licensed in North America by Yen Press.

Thirty-seven-year-old Satoru Mikami is a typical corporate worker, who is perfectly content with his monotonous lifestyle in Tokyo, other than failing to nail down a girlfriend even once throughout his life. In the midst of a casual encounter with his colleague, he falls victim to a random assailant on the streets and is stabbed. However, while succumbing to his injuries, a peculiar voice echoes in his mind, and recites a bunch of commands which the dying man cannot make sense of