"Not My Fault" is a song by American singer Reneé Rapp and American rapper Megan Thee Stallion from the 2024 Mean Girls musical film adaptation, in which Rapp portrays Regina George. The song was written by the artists and the Broadway musical's original composer Jeff Richmond and original lyricist Nell Benjamin, alongside Ryan Tedder, Alexander 23, Billy Walsh, and Jasper Harris and was released on December 15, 2023, as the lead single for the film soundtrack. The disco-funk pop rap song became the most commercially successful single off the soundtrack and a moderate chart success, peaking at number 2 on the Billboard Bubbling Under Hot 100 and charting in the UK and Canada at numbers 61 and 82, respectively.
It is one of the two songs written specially for the film, with the other songs being from the original stage musical. The song plays during the end credits scene and is the only song from the soundtrack that is not used as a musical number.