Casanova's Henrietteʔ

Casanova had a 3-month affair with a woman he calls Henriette in his memoirs. He was 23, she was older, and when they first met in Cesena she was dressed as a soldier (passing herself off as a man), apparently running away from an unhappy marriage.

At these words I saw coming out of the bed-clothes a lovely head, with dishevelled hair, and a blooming, laughing face which, although it was crowned with a man’s cap, left no doubt that the captain’s friend belonged to that sex without which man would be the most miserable animal on earth. - Casanova’s memoirs, Venetian Years, Chapter  XXII

It seems obvious she had an enormous effect on Casanova. After spending time in Parma, she ended the relationship in Geneva, but later they stayed in touch (by letters) although they never met in person again. There seem to be several candidates for who she was, but here are the main two.

The first is Adélaide de Gueidan. That's her (above) in a painting "Adélaïde de Gueidan et sa sœur au clavecin" ("Adelaide de Gueidan and her Younger Sister on Cembalo" (harpsichord) by Claude Arnulphy, circa 1735-40.

The second theory theory is that she was Jeanne Marie d'Albert de Saint Hippolyte, and above is a painting we have that might be of her, again by Arnulphy.