Ernest Rouart (Paris, 1874 – Paris, 1942) was a French painter, illustrator, engraver, and art collector.
He was the son of Henri Rouart and the brother of Eugène Rouart. He married Julie Manet, the daughter of Berthe Morisot and Eugène Manet. With her wife, he offered many artworks to the Musée du Louvre and the Musée d’Orsay, and contributed to promote Manet's, Degas's, and Morisot's artworks with important exhibitions. He studied mathematics, but he soon changed his mind and decided to dedicate himself to art and to painting in particular. Edgar Degas, who was one of the closest friends of Ernest Rouart, introduced him to painting. Degas introduced him to Julie Manet, who eventually became his wife; they lived at Rue de Villejust, where also Jeanne Gobillard and her husband Paul Valéry, a friend of Degas, lived. Ernest Rouart was also an important art collector: he acquired many Impressionist collections and, during the War, he obtained the permission to sell Degas's works. In 1899, he participated in the Société Nationale des Beaux-Arts, the Salon des Indépendants, and the Salon of the Teilleries.