Mayoi Neko Overrun! (Japanese: 迷い猫オーバーラン!, Hepburn: Mayoi Neko Ōbāran!, "Stray Cat Overrun!") is a Japanese light novel series written by Tomohiro Matsu. Twelve volumes were published by Shueisha between 2008 and 2012 under their Super Dash Bunko imprint. The first nine feature illustrations by Peco, with Yasu, Hekiru Hikawa, and Misato Mitsumi then illustrating one each. "Mayoi Neko" translates as "Stray Cats", referring to the name of the cafe around which the story develops, and alluding to the orphans and other "stray" characters who collect there. It is also the name of a school club for helping people in the story.

The Mayoi Neko Overrun! novels have sold over two million copies. A manga adaptation by Kentaro Yabuki was serialized in Shueisha's Jump SQ. and Jump SQ.19 magazines from January 4 to October 4, 2010. An anime television series adaptation animated by AIC aired on Tokyo MX and BS11 from April 6 to June 29, 2010.