"Lucy in the Sky with Diamonds" is a song by the English rock band the Beatles from their 1967 album Sgt. Pepper's Lonely Hearts Club Band. It was written primarily by John Lennon with assistance from Paul McCartney, and credited to the Lennon–McCartney songwriting partnership. Lennon's son Julian inspired the song with a nursery school drawing that he called "Lucy – in the sky with diamonds". Shortly before the album's release, speculation arose that the first letter of each of the nouns in the title intentionally spelled "LSD", the initialism commonly used for the hallucinogenic drug lysergic acid diethylamide. Lennon repeatedly denied that he had intended it as a drug song, and attributed the song's fantastical imagery to his reading of Lewis Carroll's Alice in Wonderland books.

Sgt. Pepper's Lonely Hearts Club Band is the eighth studio album by the English rock band the Beatles. Released on 26 May 1967, Sgt. Pepper is regarded by musicologists as an early concept album that advanced the roles of sound composition, extended form, psychedelic imagery, record sleeves, and the producer in popular music. The album had an immediate cross-generational impact and was associated with numerous touchstones of the era's youth culture, such as fashion, drugs, mysticism, and a sense of optimism and empowerment. Critics lauded the album for its innovations in songwriting, production and graphic design, for bridging a cultural divide between popular music and high art, and for reflecting the interests of contemporary youth and the counterculture.