Isabelle de Montolieu was born Elisabeth Jeanne Pauline Polier de Bottens and always known as Isabelle. She was born in Lausanne, Switzerland, a daughter of Antoine-Noé Polier, seigneur de Bottens, a Protestant theologian and writer said to have been a friend of Voltaire, and his wife Elizabeth-Antoinette-Suzanne de Lagier-de Pluvianes. Her sister Jeanne-Françoise Polier de Bottens also became a writer. At age 11, Isabelle met Jean-Jacques Rousseau and was greatly influenced by his writings. She published a story about him many years later called Le Serin de Jean-Jacques Rousseau (1815). In 1769, at age 18, she married Benjamin de Crousaz, with whom she had a son. After her husband died six years later, she wrote her first novel Caroline de Lichtfield (1786), an instant bestseller that stayed in print for 100 years. She became friends with Stéphanie-Félicité, Madame de Genlis, and Edward Gibbon, who helped her in her writing career. She translated more than 100 works from other languages into French, including the first French translation of Jane Austen's novels Sense and Sensibility and Persuasion. In 1786, she married Baron Louis de Montolieu, a French aristocrat from an ancient Languedoc family, 20 years her senior. It is under her second married name that she is known to history.