"I Did Something Bad" is a song by the American singer-songwriter Taylor Swift, taken from her sixth studio album, Reputation (2017). The song was written by Swift and its producers, Max Martin and Shellback. It features a heavy electronic production that combines electro-trap, grunge and EDM elements, incorporating manipulated vocals and electronic instruments. The lyrics are about Swift's lack of remorse after acknowledging her allegedly wrongful behaviors that caused a sensation, inspired by the female characters Sansa and Arya Stark of the fantasy series Game of Thrones.

Reputation is the sixth studio album by the American singer-songwriter Taylor Swift. It was released on November 10, 2017, as her last album with Big Machine Records. She conceived Reputation as a response to the media scrutiny on her private life and public image after her previous album, 1989 (2014), propelled her toward global stardom.