Between 1846 and 1853, Bonnat lived in Madrid, Spain, where his father ran a bookshop. During this period, young Bonnat would often copy engravings of artworks made by the Old Masters, which was a crucial factor in developing his passion for art and enthusiasm for drawing. His earliest formal artistic training was under the teachings of Spanish painter Raimundo de Madrazo y Garreta.
Now in Paris, Bonnat worked in the ateliers of history painters Leon Cogniet and Paul Delaroche. He quickly became recognized and a rather fashionable portraitist, never working without a commission. Such portraits show an evident influence of several Spanish masters, such as Jusepe de Ribera, Velazquez, as well as the Flemish Van Dyck, and the Italian Titian. These characteristics, which opposed the Academicism and Neo-Classicism, placed Bonnat in the vanguard of the 1850s French painting.
In the late 1850s, he spent three years in Rome, where he befriended painters Gustave Moreau, Jean-Jacques Henner, as well as the sculptor Henri Chapu. He also tried repeatedly to win de Prix de Rome. However, he would only achieve the second prize.
In 1869, he was awarded the Legion of Honor, the highest honor to receive from the French government, he was 36 years old, a quite young age for such an honor. He became Grand Officer 13 years later. Also, in 1882, Bonnat became a professor at the Ecole des Beaux-Arts in Paris. Several distinguished artists came under his teachings, such as John Singer Sargent, Henri de Toulouse-Lautrec, Thomas Eakins, Edvard Munch, and Georges Braque, to name only a few.
In his late years, instead of getting stagnated in his old ways of painting, Bonnat continued to evolve his art. He would now execute his paintings much more freely, scratching with the brush as well as with the spatula, he also began to create more colorful compositions.
He created a museum in Bayonne, his hometown, as a token of gratitude and form of repaying the city’s support.
Bonnat never married. Neither did have any offspring. He would spend most of his life living with his mother and sister.
Leon Bonnat died in September 1922, in the city of Monchy-Saint-Eloi.