Rosa Bonheur (born Marie-Rosalie Bonheur; 16 March 1822 – 25 May 1899) was a French painter, sculptor and animalier. Her paintings include Ploughing in the Nivernais, first exhibited at the Salon of 1849, and now in the Musée d'Orsay in Paris, and The Horse Fair (in French: Le marché aux chevaux), which was exhibited at the Salon of 1853 (finished in 1855) and is now in the Metropolitan Museum of Art in New York City. Bonheur was widely considered to be the most famous female painter of the nineteenth century. She made sculptures in a realist style.

It has been said that Bonheur was openly lesbian, as she lived with her partner Nathalie Micas for over 40 years until Micas's death. After that she lived with American painter Anna Elizabeth Klumpke. However, others assert that nothing supports this speculation.

Bonheur was born on 16 March 1822 in Bordeaux, Gironde, the oldest child in a family of artists. Her mother was Sophie Bonheur (née Marquis), a piano teacher; she died when Rosa was eleven. Her father was Oscar-Raymond Bonheur, a landscape and portrait painter who encouraged his daughter's artistic talents. Though of Jewish origin, the Bonheur family adhered to Saint-Simonianism, a Christian socialist sect that promoted the education of women alongside men. Bonheur's siblings included the animal painters Auguste Bonheur and Juliette Bonheur, as well as the animal sculptor Isidore Jules Bonheur. Francis Galton used the Bonheurs as an example of the eponymous "Hereditary Genius" in his 1869 essay.

Bonheur moved to Paris in 1828 at the age of six with her mother and siblings, after her father had gone ahead of them to establish a residence and income there. By family accounts, she had been an unruly child and had a difficult time learning to read, though she would sketch for hours at a time with pencil and paper before she learned to talk. Her mother taught her to read and write by asking her to choose and draw a different animal for each letter of the alphabet. The artist credited her love of drawing animals to these reading lessons with her mother.

At school, she was often disruptive and was expelled numerous times. After a failed apprenticeship with a seamstress at the age of twelve, her father undertook her training as a painter. Her father allowed her to pursue her interest in painting animals by bringing live animals to the family's studio for studying.

Following the traditional art school curriculum of the period, Bonheur began her training by copying images from drawing books and by sketching plaster models. As her training progressed, she made studies of domesticated animals, including horses, sheep, cows, goats, rabbits, and other animals in the pastures around the perimeter of Paris, the open fields of Villiers near Levallois-Perret, and the still-wild Bois de Boulogne. At fourteen, she began to copy paintings at the Louvre. Among her favorite painters were Nicolas Poussin and Peter Paul Rubens, though she also copied the paintings of Paulus Potter, Frans Pourbus the Younger, Louis Léopold Robert, Salvatore Rosa, and Karel Dujardin.

She studied animal anatomy and osteology in the abattoirs of Paris and dissected animals at the École nationale vétérinaire d'Alfort, the National Veterinary Institute in Paris. There, she prepared detailed studies that she later used as references for her paintings and sculptures. During this period, she befriended the father-and-son comparative anatomists and zoologists, Étienne Geoffroy Saint-Hilaire and Isidore Geoffroy Saint-Hilaire.

Bonheur's first major success can be attributed to The Horse Fair, which was first displayed at the Paris Salon in 1853. The painting was started in 1851 and completed in 1855. It measures eight by sixteen feet (2.4 by 4.9 m) and depicts the horse market held in Paris, on the tree-lined boulevard de l'Hôpital, near the Pitié-Salpêtrière Hospital, which is visible in the painting's background. There is a reduced version that can be found in the National Gallery located in London. Bonheur had been displaying her work at the Paris Salon for several years before displaying The Horse Fair, earning medals and smaller praise. This even resulted in the commissioning of Ploughing in the Nivernais from the state, which was exhibited in 1849 and is now on display in the Musée d'Orsay located in Paris. Due to The Horse Fair sparking debate and controversy among critics and collectors when it was first displayed at the Paris Salon, it allowed Bonheur to create a public image and insert herself into the international art world. One such debate was that Comte de Nieuwerkerke (1811 - 1892) implied that Bonheur had been commissioned by the state to create the work, though there is no known documentation to back said implication, and Bonheur herself went through the effort of discrediting it. In 1856, Bonheur traveled to England and Scotland with Micas, where she met Queen Victoria, John Ruskin, and other major British artists. In Scotland, she completed sketches and studies for later works such as Highland Shepherd, completed in 1859, The Highland Raid, completed in 1860, and other paintings. These pieces depicted a way of life in the Scottish Highlands that had disappeared a century earlier, and had an enormous appeal to Victorian sensibilities.