Thérèse Levasseur, also known as Thérèse Le Vasseur and Thérèse Lavasseur, was the domestic partner of French philosopher Jean-Jacques Rousseau.
She was a barely-literate seamstress who may have borne him as many as five children, all of whom were given away to Enfants-Trouvés foundling home, the first in 1746 and the others in 1747, 1748, 1751, and 1752.
They met in March 1745, at the hotel where he was staying, and she was employed as a chambermaid, and, although they never married, she remained his companion until his death. They went through a legally invalid marriage ceremony at Bourgoin on August 29, 1768. Therese provided Rousseau with support and care, and when he died, she became the sole heiress of his belongings, including manuscripts and royalties.
After Rousseau's death in 1778, she married valet Jean-Henri Bally in November 1779. They lived together in Le Plessis-Belleville until her death in 1801.
Mount Lavasseur, Alaska, is named after her, for its proximity to Rousseau Peak.