"This Boy" is a song by English rock band the Beatles, written by John Lennon (credited to Lennon–McCartney). It was released in November 1963 as the B-side of the British Parlophone single "I Want to Hold Your Hand". It also appears as the third track on side one of the 1964 U.S album Meet the Beatles!. The Beatles performed it live on 16 February 1964 for their second appearance on The Ed Sullivan Show.

"This Boy" was remastered for compact disc by George Martin and released in 1988 on the Past Masters, Volume One compilation. On 9 September 2009 it was re-released on the two CD set Past Masters, as part of the remastering of the original Beatles' catalogue, and was included in The Beatles Stereo Box Set and in The Beatles in Mono box set.

Its composition was an attempt by Lennon at writing a song in the style of Motown star Smokey Robinson, specifically his song "I've Been Good To You", which has similar circular doo-wop chord changes, melody and arrangement. The tune and arrangement also draws from "You Don't Understand Me", a B-side to a Bobby Freeman single.Paul McCartney cites the Teddy Bears' 1958 hit "To Know Him Is To Love Him" as also being influential. Lennon, McCartney, and George Harrison join together to sing an intricate three-part close harmony in the verses and refrain (originally the middle eight was conceived as a guitar solo, but altered during the recording process) and a similar song writing technique is exercised in later Beatles songs, such as "Yes It Is" and "Because". The song, in D major, revolves around a 1950s-style I-vi-ii-V doo-wop sequence in 12/8 time before moving to the harmonically complex middle eight (G-F#7-Bm-D7-G-E7-A-A7) and back again for the final verse and fade-out. William Mann describes the song as, "harmonically...one of their most intriguing, with its chains of pandiatonic clusters"

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