O’Murphy is born in Rouen, France on October 21, 1737 as the youngest of twelve children of Daniel Morfi and Marguerite Iquy, a family of Irish origin. Her parents have well-known criminal histories. Her father was involved in a case of espionage and blackmail while her mother was accused of prostitution and theft. She and her sisters are also known for being involved in prostitution.
Contemporary and modern historiography believe O’Murphy is the very young model who posed for the Jeune Fille allongée (Reclining Girl), of François Boucher, a painting famous for its undisguised eroticism, dating from 1752. Two versions of this painting have survived, both conserved in Germany, one in the Alte Pinakothek at Munich and the other in the Wallraf-Richartz Museum at Cologne.
The term petite maîtresse (little mistress) is given to Louis XV’s mistresses that are not formally presented at court, and unlike the official mistress (maîtresse-en-titre) do not have an apartment in Palace of Versailles. Generally recruited by the King’s valets in Paris surroundings, if their affair lasts more than a single night, they are placed in a group of houses in the district of Parc-aux-Cerfs in Versailles, or close to other royal residences. O’Murphy resides there for two years, from 1753 to 1755.
After a miscarriage in mid-1753 which almost kills her, O’Murphy gives birth to Louis XV’s illegitimate daughter, Agathe-Louise de Saint-Antoine de Saint-André, born in Paris on June 20, 1754. The King, who does not want to recognize the offspring born from petites maîtresses and brief affairs, orders that the newborn must be immediately placed in care of a wet nurse. Subsequently, Agathe-Louise is sent to the Couvent de la Présentation, where she is raised.
After serving as a mistress to the King for almost two years, O’Murphy makes a mistake that is common for many courtesans, that of trying to replace the official mistress. She unwisely tries to unseat the longtime royal favorite, Madame de Pompadour. This ill-judged move quickly results in her downfall at court. In November 1755 she is expelled at night from her home at Parc-aux-Cerfs, repudiated by the King, and sent far away from Versailles.
O’Murphy hastily marries Jacques Pelet de Beaufranchet, Seigneur d’Ayat on November 25, 1755. Soon after she becomes pregnant. Her first child, a daughter named Louise Charlotte Antoinette Françoise Pelet de Beaufranchet, is born on October 30, 1756 (she dies at the age of two). Thirteen months later, on November 5, 1757, her husband is killed in action at the Battle of Rossbach. Seventeen days after his death she gives birth a second child, a son, Louis Charles Antoine de Beaufranchet, the later Comte de Beaufranchet and General under the Republic.
On February 19, 1759, O’Murphy marries François Nicolas Le Normant, Comte de Flaghac and Receiver General of Finance in Riom, a divorcee with three children. From this marriage, she gives birth to a daughter, Marguerite Victoire Le Normant de Flaghac on January 5, 1768, who, according to one theory, could be another illegitimate daughter of Louis XV. François Le Normant dies on April 24, 1783.
During the Reign of Terror O’Murphy is imprisoned as a “suspect,” under the name of O’Murphy, at Sainte-Pélagie Prison and later at the English Benedictine convent in Paris. After her release she marries Louis Philippe Dumont, a moderate MP for Calvados in the National Convention and twenty-eight years her junior, on June 19, 1795. This union quickly fails, and after almost three years, they divorce on March 16, 1798. She never marries again.
Marie-Louise O’Murphy dies in Paris on December 11, 1814 aged 77, at the home of her daughter Marguerite Le Normant.