"Eight Days a Week" is a song by the Beatles written by Paul McCartney and John Lennon based on McCartney's original idea. The song was issued in the United Kingdom in December 1964 on the album Beatles for Sale. In the United States, issued in February 1965 as a single with the B-side "I Don't Want to Spoil the Party", it went to No. 1 for two weeks on 13–20 March 1965. The song was also issued in June 1965 on the U.S. album Beatles VI and reissued worldwide in 2000 on the Beatles number one compilation album 1. WLS ranked the song at #8 for all of 1965.

Paul McCartney has attributed the inspiration of the song to at least two different sources. In a 1984 interview with Playboy, he credited the title to Ringo Starr, who was noted for his malapropisms, which are credited as the source of other song titles (such as "A Hard Day's Night" and "Tomorrow Never Knows"):

LINDA: Ringo also said, 'Eight days a week.'
PAUL: Yeah, he said it as though he were an overworked chauffeur. (in heavy accent) 'Eight days a week.' (laughter) When we heard it, we said, 'Really? Bing! Got it!'

However, he has also credited the title to an actual chauffeur who once drove him to Lennon's house in Weybridge:

I usually drove myself there, but the chauffeur drove me out that day and I said, 'How've you been?' – 'Oh working hard,' he said, 'working eight days a week.'

In a 2016 Q&A interview alongside Ringo Starr and Ron Howard, in preparation for the release of the documentary The Beatles: Eight Days a Week – The Touring Years, he reiterated that he had heard it from a chauffeur who was driving him to Lennon's house whilst he was banned from driving.

"Eight Days a Week" is the first song which the Beatles took into the studio unfinished to work on the arrangement during the session, a practice which would later become common for the band. The song was mainly recorded in two recording sessions on 6 October devoted exclusively to this song, which lasted nearly seven hours with a fifteen-minute break in between. Lennon and McCartney tried several ideas for the intro and outro of the song. The first take featured a simple acoustic guitar introduction. The second take introduced an "oo"-ing vocal that was experimented with until the sixth take, when it was abandoned in favour of the final guitar intro. The final outro (along with unused intro takes) was recorded separately on 18 October. The final version of the song incorporated another Beatles' first and pop music rarity: the song begins with a fade-in, as opposed to the common fade-out ending. The instrumentation includes acoustic guitar, electric guitar, drums, bass and overdubbed handclaps. The fade-in and coda both include more guitar overdubs.

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