Gabrielle Émilie Le Tonnelier de Breteuil, Marquise du Châtelet-Laumont (December 17, 1706 - September 10, 1749) was a French mathematician, physicist and author.

In a society where nobility disliked the notion of education for their daughters arose one of the great mathematicians of the 18th century, Frenchwoman, Émilie du Châtelet. Born in Paris, she grew up in a household where the art of courting was the only way one could mold a place in society. During her early childhood, she began to show such promise in the area of academics that soon she was able to convince her father that she needed attention. Provided with a relatively good education for the time, she studied and soon mastered Latin, Italian and English. She also studied Tasso, Virgil, Milton and other great scholars of the time.

In spite of her talents in the area of languages, her true love was mathematics. Her study in this area was encouraged by a family friend, M. de Mezieres, who recognized the young lady's talent. Émilie du Châtelet's work in mathematics was rarely original or as captivating as that of other female mathematicians but it was substantive. The fact that it was accomplished in the first place is in itself remarkable.

Du Châtelet's astuteness was prominent in other areas as well. She was described as being somewhat of a "passionate nature", never lacking for romantic attachments either before or after her marriage. At the age of nineteen she married the thirty-four-year-old Marquis du Chatelet. During the first two years of their marriage, she gave birth to a boy and a girl, and later the birth of another son followed when she was twenty-seven. Neither children nor her husband deterred her from fully indulging in the social life of the court.

Du Châtelet not only refused to give up mathematics but she engaged the best tutors to help her in her study. She also conquered the heart of Voltaire, one of most intriguing and brilliant scholars of this time. Some of her most significant work came from the period she spent with Voltaire at Cirey-sur-Blaise . For the two scholars this was a safe and quiet haven distant from the turbulence of Paris and court life. As Voltaire notes "We long employed all our attention and powers upon Leibniz and Sir Isaac Newton; Mme du Chatelet attached herself first to Leibniz, and explained one part of his system in a book exceedingly well written, entitled Institutions de physique ."

However she soon abandoned the work of Leibniz and applied herself to the discoveries of Newton. She was extremely successful in translating his whole book on the principles of mathematics into French. She also added to this book an "Algebraic Commentary" which very few general readers understood.

One of Émilie du Châtelet's most significant tutors was Pierre Louis Maupertuis, a renowned mathematician and astronomer of the time. As a student her curiosity and stubbornness caused her to place impossible demands on her tutors. As Lynn Osen notes, "Her swift mind outpaced them, her irregular hours disrupted their lives, her rigorous questions were frequently impossible to answer."

Such behavior caused her to get into a dispute with another of her tutors, Samuel Koenig , about the subject of the infinitely small. This dispute subsequently ended their friendship and association.

In 1740 when Émilie du Châtelet's book Institutions de physique was published, Koenig started a rumor that the work was merely a rehash of his lessons with her. Of course this infuriated Emilie, and for help she turned to the Academy of Sciences and Maupertuis, with whom she had discussed these ideas long before she engaged Koenig as her tutor. The knowledgeable scientists of the time were aware of her capabilities of performing the work. However she did not feel that she had received the support she deserved. This was the first time she felt that being a woman really worked against her.

The years Emilie spent with Voltaire at Cirey were some of the most productive years of her life. Their scholarly work was very intense. When there were no guests both of them remained tied to their desks. A servant who worked at Cirey at this time noted "Mme du Chatelet passed the greater part of the morning with her writings, and did not like to be disturbed. When she stopped work, however, she did not seem to be the same woman. The serious air gave place to gaiety and she gave herself up with the greatest enthusiasm to the delights of the society." She frequently claimed that the only pleasures left for a woman when she is old is study, gambling, and greed.

In the spring of 1748, Émilie du Châtelet met and fell in love with the Jean François de Saint-Lambert, an officer in the guard of King Stanislaus I of Poland and poet. This affair, however, did not destroy her friendship with Voltaire. Even when he found out that she was carrying Saint-Lambert's child, Voltaire was there to support her. With the help of Voltaire and Saint-Lambert, she was able to convince her husband that it was his child she was carrying.

During the course of her pregnancy in 1749 she finished her work with Clairaut, an old friend with whom she had been studying; however, her book on Newton still awaited completion. She was determined to finish it and with that goal she took on a very regimented lifestyle of only work. She would rise early in the morning, working until late at night. She gave up most of her social life and saw only few friends.

In early September of 1749, she gave birth to a baby girl. As Voltaire describes it: "The little girl arrives while her mother was at her writing desk, scribbling some Newtonian theories, and the newly born baby was placed temporarily on a quarto volume of geometry, while her mother gathered together her papers and was put to bed." For several days, Emilie seemed happy and content. On September 10, 1749 she died suddenly, however.

Émilie du Châtelet's death was soon followed by the death of the baby girl. As Osen notes, "Voltaire, who was with her at the end, was distraught in tears. He stumbled from the room and fell at the outside door."

Du Châtelet died at the age of forty-three. As many authors note, during the course of her short life, Emilie was a truly unique woman and scholar. Among her greatest achievements were her Institutions de physique and the translation of Newton's Principia, which was published after her death along with a "Preface historique" by Voltaire. In short "she lived a life at a full tilt like a spirited healthy child." She managed to maintain her confidence and position in Paris society while pursuing her love for mathematics. Émilie du Châtelet was one of many women whose contributions have helped shape the course of mathematics.

More than half of the twenty chapters of her book are concerned with science, that is physical, i.e. matter, gravity, weight, equilibrium etc.. 18th century France found itself contemplating the interconnectedness of metaphysics and physics at the time of Émilie's writing. In respect to matters of metaphysics she claimed: "it is certain that there are a number of points in metaphysics which lend themselves to demonstrations just as rigorous as the demonstrations of geometry, even if they are different in kind." Thus, included in her introduction to the explanation of the work of Newton was a discussion of the metaphysics of Leibniz. "Émilie's exposition of German Philosophy was remarkably clear." Mme du Chatelet was interested in bringing Metaphysics into the picture and provide it to prove the 'sufficient reason' for the universe as described by scientists'.

From the most physical of science to the existence of God, Institutions de Physique was a major accomplishment. Émilie's interest in the principle of sufficient reason and Leibniz' attempt to explain the origin of evil may have played a role in Voltaire's discussion of these topics and his ridicule of Leibniz in Candide. Voltaire agreed with Pierre Bayle, that it was not possible, as Leibniz believed, to explain rationally the role which evil plays in the divine plan.

She was related to Louis-Auguste, baron de Breteuil, who was the last Prime Minister of King Louis XVI in 1789.