"Diary" is a song by American singer-songwriter Alicia Keys from her second studio album, The Diary of Alicia Keys (2003). Written by Keys and Kerry Brothers, Jr. and produced by Keys, the song features the American group Tony! Toni! Toné! on bass, piano, guitar, organ and Wurlitzer, while Jermaine Paul provides uncredited additional vocals. It was released on May 24, 2004, as the album's third single. At one time, "Diary" had been released as a double A-side with "If I Ain't Got You".

Alicia Augello Cook, known professionally as Alicia Keys, is an American singer and songwriter. A classically trained pianist, Keys began composing songs when she was the age of 12 and was signed by Columbia Records at the age of 15. After disputes with the label, she signed with J Records to release her debut studio album, Songs in A Minor (2001). Met with critical acclaim and commercial success, the album sold over 12 million copies worldwide and won five awards at the 44th Annual Grammy Awards. It contained the Billboard Hot 100-number one single "Fallin'." Her second album, The Diary of Alicia Keys (2003) was met with continued success, selling eight million units worldwide and spawning the singles "You Don't Know My Name", "If I Ain't Got You", and "Diary". Its release earned an additional four Grammy Awards.