Hot N Cold

"Hot n Cold" is a song by American singer Katy Perry. The song was written and composed by Dr. Luke, Max Martin, and Perry for her major mainstream debut album, One of the Boys. The track was released as the album's second single. It is about an unstable heterosexual romantic relationship, told from her point of view. The chorus uses several antonyms to describe her partner's bipolar mood swings, with the verses describing how they affect the couple's life together.

The single reached number three on the Billboard Hot 100, making it Perry's second consecutive top three single, after her previous worldwide hit "I Kissed a Girl". The single has also become Perry's second top five single in the United Kingdom, Australia, Ireland and New Zealand, and topped the charts in Finland, Germany, Canada, Norway, Spain and Denmark, and has topped the charts in 15 countries.

As of September 2011, "Hot n Cold" has sold over five million digital downloads. Perry sang the song in Simlish for the soundtrack of Sims 2: Apartment Life. In 2010, Perry performed a version of the song with Elmo intended for the children's television show Sesame Street (to teach children about opposites) which was released on websites such as YouTube. However, the producers of Sesame Street decided not to air the segment on the show after receiving complaints that Perry's revealing wardrobe was not appropriate for children. Perry alluded to the controversy later that week on Saturday Night Live by wearing a low cut Elmo t-shirt with a short skirt.