Gautreau was born Virginie Amélie Avegno in New Orleans, Louisiana, on 29 January 1859, the daughter of Anatole Placide Avegno (3 July 1835 – 7 April 1862) and Marie Virginie de Ternant of Parlange Plantation, a descendant of French nobility. She had a sister, Valentine, who died of yellow fever. Her parents were white Creoles; her father was the son of Philippe Avegno (originally Italian) and Catherine Genois.  Her father Anatole Avegno served as a major in the Confederate Army during the American Civil War; he died in 1862 in the Battle of Shiloh. He was the commander of the Avegno Zouaves of New Orleans, a cosmopolitan battalion which had soldiers from a wide variety of ethnic backgrounds including French, Spanish, Mexican, Irish, Italian, Chinese, German, Dutch, and Filipino soldiers.  In 1867, when Virginia was eight, her widowed mother moved with her to France. The girl was educated in Paris and introduced to high French society.  Virginie Avegno became one of Paris’s conspicuous beauties, as she was a pale-skinned brunette with fine, cameo-like features and an hourglass figure. She was known to use lavender-colored face and body powder to enhance her complexion, to dye her hair with henna, and to color her eyebrows. She attracted much admiration due to her elegance and style.  She married Pierre Gautreau, a French banker and shipping magnate. She had a daughter named Louise Gautreau (1879-1911).

She posed for paintings by several noted 19th-century painters, including Gustave Courtois and Antonio de La Gandara.  Most famously, she was the model for John Singer Sargent’s Portrait of Madame X. The painting created a cultural scandal when it was exhibited in 1884 at the Paris Salon. The suggestiveness of the portrait and the style of clothing were considered scandalous, as well as publicizing Gautreau’s reputation. Such a high-class woman would not usually be a model. The scandal caused Gautreau to retire for some time from society.  Antonio de La Gandara painted a full-length portrait of her, entitled Madame Gautreau (1898). In tonality of colors, privacy of her face, and style of her dress, it was more conservative than Sargent’s painting.  Gautreau died in Cannes on 25 July 1915. She was buried in the Gautreau family crypt at their Chateau des Chênes in Saint-Malo, Brittany.