Andre Moreau vs. Noel, Marquis de Maynes, final fight from Scaramouche (1952)

before there was "The Princess Bride" there was Scaramouche (1952), a lush Hollywood adventure film about a young man, Andre Moreau (Stewart Granger), who embarks on a protracted plan of revenge against a nobleman and expert swordsman, Noel, Marquis de Maynes (Mel Ferrer), who murdered Andre's friend. Andre disguises himself as a comical performer, Scaramouche, but interrupts a performance in order to challenge the Marquis to a final showdown.

the resulting swordfight lasts about six minutes of screen time and was considered for a long while to be the record-holder in this regard.