Léon Joseph Florentin Bonnat was a French painter, Grand Officer of the Légion d'honneur and professor at the Ecole des Beaux Arts.

Bonnat was born in Bayonne, but from 1846 to 1853 he lived in Madrid, where his father owned a bookshop. While tending his father's shop, he copied engravings of works by the Old Masters, developing a passion for drawing. In Madrid he received his artistic training under Madrazo. He later worked in Paris, where he became known as a leading portraitist, never without a commission. His many portraits show the influence of Velázquez, Jusepe de Ribera and other Spanish masters, as well as Titian and Van Dyke, whose works he studied in the Prado, which placed him at the forefront of painting in France in the 1850s, opposing neoclassicism and academicism. Following the period in Spain, Bonnat worked the studios of the history painters Paul Delaroche and Leon Cogniet (1854) in Paris.

Despite repeated attempts, he failed to win the prix de Rome, finally receiving only a second prize. However, a scholarship from his native Bayonne and support from the Personnaz family allowed him to spend three years in Rome (1858–60) independently where he and Antonin Personnaz became lifetime friends. During his stay in Rome, he also became friends with Edgar Degas, Gustave Moreau, Jean-Jacques Henner and the sculptor Henri Chapu.

Bonnat won a medal of honour in Paris in 1869, going on to become one of the leading artists of his day. Bonnat went on to win the Grand Officer of the Légion d'honneur and became a professor at the Ecole des Beaux Arts in 1882. Bonnat was quite popular with American students in Paris. In addition to his native French, he spoke Spanish and Italian and knew English well, to the relief of many monolingual Americans. In May 1905 he succeeded Paul Dubois as director of the Ecole des Beaux-Arts. Julius Kaplan characterised Bonnat as "a liberal teacher who stressed simplicity in art above high academic finish, as well as overall effect rather than detail." Bonnat's emphasis on overall effect on the one hand, and rigorous drawing on the other, put him in a middle position with respect to the Impressionists and academic painters like his friend Jean-Léon Gérôme. In 1917, Bonnat was elected into the National Academy of Design as an Honorary Corresponding member.