"You Can't Do That" is a song written by John Lennon (credited to Lennon–McCartney) and released by the Beatles as the B-side of their sixth British single "Can't Buy Me Love".

One of Lennon's semi-autobiographical songs, "You Can't Do That," "contradicted the genial tone with its tense threats, sexual paranoia and nagging, dragging groove," according to Robert Sandall. The song's jealousy theme was re-visited in other Lennon compositions, such as "Run for Your Life" and "Jealous Guy". Influenced by the then relatively unknown Wilson Pickett the song is rooted in the twelve-bar blues form, with Lennon introducing a discordant Sharp 9th (F) on the D7th chord, pointedly emphasising "…I told you before…" and then pushing this note for the exasperated "Oh!" before resolving to the song's key of G. Lennon also played the guitar solo, which he conceived. The song reflected Lennon's love for hard-edged American R&B—"a cowbell going four in the bar and the chord going chatoong!" as he put it.

George Harrison wrote the intro and outro guitar riff in the studio according to Tom Petty in Rolling Stone Magazine. When asked by Petty how he came up with it, Harrison recalled "I was just standing there [in the studio] and thought, 'I've got to do something!'".

With filming due to begin on A Hard Day's Night film director Dick Lester needed the Beatles to provide him with original material ahead of production and "You Can't Do That" was selected to be part of the Scala Theatre "live performance" scene in the film, but was dropped from the final cut along with "I'll Cry Instead" and "I Call Your Name." The recording took nine takes to complete, and was considered for the A-side of their next single until McCartney wrote "Can't Buy Me Love."

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