"Because" is a song written by John Lennon (credited to Lennon–McCartney) and recorded by the Beatles in 1969. It features a prominent three-part vocal harmony by Lennon, Paul McCartney, and George Harrison, overdubbed twice to make nine voices in all. It first appeared on Abbey Road (1969), immediately preceding the extended medley on side two of the record.

The song begins with a distinctive electric harpsichord intro played by producer George Martin. The harpsichord is joined by Lennon's guitar (mimicking the harpsichord line) played through a Leslie speaker. Then vocals and bass guitar enter.

"Because" was one of few Beatles recordings to feature a Moog synthesiser, played by George Harrison. It appears in what Alan Pollack refers to as the "mini-bridge", and then again at the end of the song.

According to Lennon, the song's close musical resemblance to the first movement of Ludwig van Beethoven's Moonlight Sonata was no coincidence: "Yoko was playing Beethoven's 'Moonlight Sonata' on the piano ... I said, 'Can you play those chords backwards?', and wrote 'Because' around them. The lyrics speak for themselves ... No imagery, no obscure references."

With regard to the controversy Lennon initiated by citing Beethoven's "Moonlight Sonata" as an inspiration, musicologist Walter Everett notes that "both arpeggiate triads and seventh chords in C♯ minor in the baritone range of a keyboard instrument at a slow tempo, move through the submediant to ♭II and approach vii dim7/IV via a common tone." But while acknowledging the unusual shared harmonies, Dominic Pedler notes that the relationship is not the result of reversing the order of the chords as Lennon suggested.

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