"Inside Out" is a song by American recording artist Britney Spears, included on her seventh studio album Femme Fatale (2011). It was written by Lukasz Gottwald, Jacob Kasher Hindlin, Mathieu Jomphe, Max Martin and Bonnie McKee whilst production was handled by Dr. Luke, Max Martin and Billboard. Musically, "Inside Out" is an electropop song that uses elements of dubstep and R&B, and has been compared to Spears' previous material on previous albums In the Zone and Circus, as well as the work of Madonna. Lyrically, the song has been described as a "sexy break-up song", while making references to her previous singles "...Baby One More Time" and "(You Drive Me) Crazy". The song received generally positive reviews from music critics, who commended its production. Due to strong digital sales of the album, "Inside Out" peaked at number fifty-nine on South Korea's Gaon International Chart.

"Inside Out" was written by Jacob Kasher Hindlin and Bonnie McKee, while additional writing and song production was done by Dr. Luke, Martin, and Billboard. A small teaser of the song was unveiled by the singer on February 19, 2011. On March 11, 2011, it leaked in full online, along with another Femme Fatale track, "(Drop Dead) Beautiful". The song was also rumored to be the second single of Femme Fatale; the information was later denied following the online leak of "Till the World Ends" on March 3, 2011, which was released instead in the next day. On August 5, 2011, Spears posted a poll on her Facebook page asking fans whether her next single should be "Criminal", "Inside Out" or "(Drop Dead) Beautiful." After the 2011 MTV Video Music Awards, she revealed to MTV News that "Criminal" was chosen as the fourth single.

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