I Knew You Were Trouble

"I Knew You Were Trouble" is a song by the American singer-songwriter Taylor Swift from her fourth studio album, Red (2012). She wrote it with its producers, Max Martin and Shellback. A dubstep and pop track, "I Knew You Were Trouble" has a production based around electric guitars and synthesizers, accentuated its refrain with a wobble bass and Swift's distorted vocals; critics found the dubstep production a radical departure from Swift's previous country pop sounds. In the lyrics, the narrator blames herself for not recognizing the warning signs of a past toxic relationship.

Big Machine, in partnership with Republic Records, released "I Knew You Were Trouble" to US pop radio on November 27, 2012, as the second pop single and the third overall from Red. The song peaked within the top 10 on record charts and received multi-platinum certifications in Australia, Austria, Canada, New Zealand, and the UK. In the US, the single peaked at number two on the Billboard Hot 100 and spent seven weeks at number one on the Pop Songs chart. Its success on pop radio inspired Swift to recalibrate her artistic identity from country for pop on her 2014 album 1989. Initial reviews were divided: positive comments found the production bold, but criticisms deemed it derivative. Retrospective opinions have regarded "I Knew You Were Trouble" as one of Swift's career-defining singles.

The music video for "I Knew You Were Trouble" premiered on MTV on December 13, 2012. Directed by Anthony Mandler, it depicts Swift with an unfaithful man and ending up alone in a desert. The video won Best Female Video at the 2013 MTV Video Music Awards and the Phenomenon Award at the 2013 YouTube Music Awards. Swift performed "I Knew You Were Trouble" at awards shows including the American Music Awards, the ARIA Music Awards, and the Brit Awards. She included it on the set lists of the Red Tour (2013–2014), the 1989 World Tour (2015), and the Eras Tour (2023–2024). After a 2019 dispute regarding the ownership of her back catalog, Swift re-recorded the song as "I Knew You Were Trouble (Taylor's Version)" for her second re-recorded album, Red (Taylor's Version) (2021).