The Lady is a young, beautiful, and wealthy woman of distinguished birth who was raised primarily in the country. Her rural upbringing makes her slightly naive but deeply curious about urban society and the different rules governing men and women. Left largely unsupervised in London, she possesses a rich imagination and an unconventional streak that prompts her to adopt the disguise of a prostitute named Fantomina to safely explore the city.

Beauplaisir is a charming, wealthy nobleman and an active man of the world. Accustomed to privilege and easy romantic conquests, he enjoys playing the role of the gallant pursuer. He is notoriously fickle and quickly loses interest in women once he believes he has won them over, a trait that drives much of the story's romantic tension.

The Lady's mother is a forceful, conventional parent who represents the strict social order of 18th-century England. She places immense value on decorum, status, and maintaining public appearances. Her absence allows her daughter the freedom to experiment with her identity, but her traditional authority hangs over the narrative.

The Aunt serves as The Lady's temporary guardian in London. She provides a respectable, stable household for her niece, completely unaware of the young woman's nighttime excursions or secret activities.