Mademoiselle de Maupin disguises herself as a man so that she can learn about men before trying to find herself one. Her masquerade is entirely successful as she's something of a tom-boy. Her new found cavalier friend takes her home to meet his widowed sister, with whom she flirts masterfully and who falls deeply and passionately in love with her. She in turn falls in love with Rosette, the widow, not sexually, but sensually, romantically and aesthetically...
The plot of the book revolves around a romantic triangle where D'Albert and his mistress Rosette are both in love with Théadore, neither of them realizing she is really mlle. de Maupin.
Gautier based his protagonist on a seventeenth century actress whose interests in members of her own sex caused parents to send their daughters to convents and over whom she fought public and illegal duels.
