"I'm Down" is a song by the Beatles written by Paul McCartney (credited to Lennon–McCartney) and first released as the B-side to the single "Help!" in 1965.

According to critic Richie Unterberger of Allmusic, "I'm Down" is "one of the most frantic rockers in the entire Beatles' catalog." McCartney told writer Barry Miles that the song and his vocal style on it were influenced by Little Richard, "I used to sing his stuff but there came a point when I wanted one of my own, so I wrote 'I'm Down.'"

The Beatles recorded "I'm Down" on 14 June 1965 in the same session as "Yesterday" and "I've Just Seen a Face".

The Beatles recorded the backing track in seven takes. The first of these takes can be heard on Anthology 2, with a quiet organ track and no backing vocals. At the beginning of the Anthology version, McCartney says, "Let's hope this one turns out pretty darn good" in a faux American accent. During the session, particularly between takes one and two, McCartney can be heard repeating the phrase "Plastic soul, man, plastic soul". He later revealed that the phrase, which the Beatles later adapted for the title of their album Rubber Soul, was used by black musicians to describe Mick Jagger.

The official release date for the "Help"/"I'm Down" single was 19 July 1965 on Capitol Records in the United States and 23 July on Parlophone in the United Kingdom. "I'm Down" was never released on an official Beatle studio album, and was only available in the US in mono as the B-side of the "Help!" single until the summer of 1976. That year, it appeared in stereo on Rock 'n' Roll Music, a compilation LP released in the US by Capitol featuring up tempo Beatles' tracks. The first CD release was in 1988 on the compilation Past Masters, Volume One, where it appeared in true stereo.

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