I’m pretty sure I’m right on this----GIGI, starring the very young AUDREY HEPBURN was on Broadway as a NON-musical many years before the LESLIE CARON musical one.
another film to broadway one—
BREAKFAST AT TIFFANY’S------as a musical, starring MARY TYLER MOORE (I think) and RICHARD CHAMBERLAIN.
ex A look at the cast albums shows the movie soundtrack was recorded in 1958, while the original Broadway cast was recorded in 1973. Hepburn did appear in the play “Gigi,” but the musical was definitely based on the movie, since it contained the same list of songs.
According to the allmusic guide:
And add “La Cage au Folles.”
A few more:
Shenandoah
The Wiz
Woman of the Year
Grand Hotel
The Goodbye Girl
Can’t believe I forget…The Full Monty!
Chaim Mattis Keller
Meet Me in St. Louis.
I think the “purist” answer to the OP is what movie musicals were adapted as subsequent stage musicals. The genre is replete with stage musical shows adapted from straight movies, books, or, in one memorable case, a pointillist painting. They’re interesting, but don’t fit the question as I read it…