An Observation Log of My Fiancée Who Calls Herself a Villainess (Japanese: 自称悪役令嬢な婚約者の観察記録。, Hepburn: Jishō Akuyaku Reijō na Konyakusha no Kansatsu Kiroku) is a Japanese light novel series written by Shiki and illustrated by Wan Hachipisu. The series was originally posted as a web novel on the Shōsetsuka ni Narō website, before Shiki removed it in March 2017. AlphaPolis later published it as a light novel under their Regina Books imprint, releasing two volumes from May to September 2017. A manga adaptation illustrated by Natsume Hasumi was serialized on AlphaPolis' Regina manga website from May 2018 to August 2021 and was compiled in six volumes. A sequel series by Shiki and Hachipisu, titled An Observation Log of My Wife Who Calls Herself a Villainess (自称悪役令嬢な妻の観察記録。, Jishō Akuyaku Reijō na Tsuma no Kansatsu Kiroku), began publication under the same imprint in April 2022, with a manga adaptation by Hasumi starting on the same website in March 2022. An anime television series adaptation produced by Ashi Productions premiered in April 2026.