One Week Friends (Japanese: 一週間フレンズ。, Hepburn: Isshūkan Furenzu.) is a manga series by Matcha Hazuki. It was serialized in Square Enix's Gangan Joker magazine between January 21, 2012, and January 22, 2015. It was first published as a one-shot manga in the magazine's September 2011 issue. The series has since been collected in seven tankōbon volumes. An anime television series adaptation by Brain's Base aired between April 6 and June 22, 2014. Sentai Filmworks licensed the rights to the show in North America and by Madman Entertainment in Australia and New Zealand. A live-action film of the same name was released in February 2017.

High schooler Yūki Hase notices that his beautiful classmate Kaori Fujimiya is always alone and seemingly has no friends. After approaching her and becoming better acquainted, Kaori reveals that every Monday she loses all memory of her friends. Despite learning this, Yūki endeavors to befriend her anew every week.