The Diary of a Middle-Aged Sage's Carefree Life in Another World (アラフォー賢者の異世界生活日記, Arafō Kenja no Isekai Seikatsu Nikki) is a Japanese light novel series written by Yasukiyo Kotobuki and illustrated by Johndee.

It began serialization on the user-generated novel publishing website Shōsetsuka ni Narō in February 2016.

Written by Yasukiyo Kotobuki, The Diary of a Middle-Aged Sage's Carefree Life in Another World began serialization on the user-generated novel publishing website Shōsetsuka ni Narō on February 7, 2016.

[2] It was later acquired by Media Factory who began releasing it with illustrations by Johndee under their MF Books light novel imprint on September 23, 2016.

[4] A spin-off light novel series, titled Arafō Kenja no Isekai Seikatsu Nikki Zero: Sword and Sorcery World, began publication under the same imprint on August 25, 2023.