Pardon me, sir, I did not mean to do it.
-Marie Antoinette’s, the last Queen of France, supposed last words before being guillotined on October 16th, 1793 during the French Revolution. She had accidentally stepped on the executioner’s foot.
Memoirs of the Sansons, Chapter XXXI ‘The Queen’:  Source written by the executioner Henri Sanson’s grandson. Makes no mention of this comment, yet other passing phrases between The Queen and her executioner are as follows:
“Have courage, madam!”
“Thank you, sir, thank you.”
He then offered to support her to the scaffold to which she was said to have replied,
“No, I am, thank Heaven, strong enough to walk that short distance.”
Memoirs of Marie Antoinette, by Madame Campan; Removal of the Queen:  Memoirs on the court of Marie Antoinette as told by her lady in waiting, Campan. The below is a quote from Alphonse de Lamartine from his Histore des Girondins, a French poet, writer, and politician who helped to compile the Memoirs with Campan:
The Queen, after having written and prayed, slept soundly for some hours. On her waking, Bault’s daughter dressed her and adjusted her hair with more neatness than on other days. Marie Antoinette wore a white gown, a white handkerchief covered her shoulders, a white cap her hair; a black ribbon bound this cap round her temples …. The cries, the looks, the laughter, the jests of the people overwhelmed her with humiliation; her colour, changing continually from purple to paleness, betrayed her agitation …. On reaching the scaffold she inadvertently trod on the executioner’s foot. “Pardon me,” she said, courteously. She knelt for an instant and uttered a half-audible prayer; then rising and glancing towards the towers of the Temple, “Adieu, once again, my children,” she said; “I go to rejoin your father.”
This is, perhaps, the origin–and though most contemporary sources of her time weren’t without bias or accusations of cake eating, this is one of the few sources painting Marie as a sympathetic figure. Unfortunately, with the politics surrounding the French Revolution, it’s a mess to separate fact from fiction.