"Favorite Girl" is a song by Canadian recording artist, Justin Bieber. The song was written and produced by D'Mile, and Antea Birchett, Anesha Birchett, and Delisha Thomas also receive writing credits. Bieber debuted the acoustic version of his song in his official YouTube account after American country pop singer Taylor Swift used Bieber's single "One Time" as background music in one of her video tour diaries. The song was later released exclusively to iTunes as the second promotional single from his debut studio release, My World on November 4, 2009.

The song is mid-tempo, and merges teen pop and R&B elements. The song debuted at number twelve and twenty-six, in Canada and the United States, respectively. It also charted at number ninety-two Australia, and at numbers seventy-six and twenty-seven in the United Kingdom, and the UK R&B chart, respectively Bieber performed the song on several occasions, most of them being the acoustic version of the song, including as a supporting act on Swift's Fearless Tour.

In August 2009, country pop singer Taylor Swift used Bieber's "One Time" as background music and music that she and her friends were dancing to in a tour video diary that she posted on her official YouTube account. In response to Swift using his song, Bieber posted an acoustic rendition of the then never-before heard "Favorite Girl" on his YouTube. When asked about his learning of Swift using his song, Bieber stated, "It was really funny because I heard about it from a fan. I watched it and it was hilarious!" Bieber and Swift then met in person at the 2009 MTV Video Music Awards, and she later invited him to be a special guest on her Fearless Tour when she returned to the United Kingdom.

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