"I Knew You Were Trouble" is a song by the American singer-songwriter Taylor Swift from her fourth studio album, Red (2012). Swift wrote the song with its producers, Max Martin and Shellback. A dance-pop, pop rock, and teen pop song with a dubstep refrain, "I Knew You Were Trouble" features electric guitars and synthesizers, with lyrics that talk about self-blame after a toxic relationship. The dubstep production divided music critics, who noted it as a radical move from Swift's previous country pop songs.

Karl Martin Sandberg, known professionally as Max Martin, is a Swedish record producer and songwriter. He rose to prominence in the late 1990s with songwriting credits on a string of hit singles, such as Britney Spears's "...Baby One More Time" (1998), the Backstreet Boys' "I Want It That Way" (1999), Céline Dion's "That's the Way It Is" (1999) and NSYNC's "It's Gonna Be Me" (2000).