Degas was born in Paris, France, into a moderately wealthy family. He was the oldest of five children of Célestine Musson De Gas, a Creole from New Orleans, Louisiana, and Augustin De Gas, a banker. His maternal grandfather Germain Musson, was born in Port-au-Prince, Haiti of French descent and had settled in New Orleans in 1810. Degas (he adopted this less grandiose spelling of his family name when he became an adult) began his schooling at age eleven, enrolling in the Lycée Louis-le-Grand. His mother died when he was thirteen, and his father and grandfather became the main influences on him for the remainder of his youth.
Degas began to paint early in life. By the time he graduated from the Lycée with a baccalauréat in literature in 1853, at age 18, he had turned a room in his home into an artist's studio. Upon graduating, he registered as a copyist in The Louvre Museum, but his father expected him to go to law school. Degas duly enrolled at the Faculty of Law of the University of Paris in November 1853, but applied little effort to his studies. In 1855 he met Jean-Auguste-Dominique Ingres, whom Degas revered and whose advice he never forgot: "Draw lines, young man, and still more lines, both from life and from memory, and you will become a good artist." In April of that year Degas was admitted to the École des Beaux-Arts. He studied drawing there with Louis Lamothe, under whose guidance he flourished, following the style of Ingres. In July 1856, Degas traveled to Italy, where he would remain for the next three years. In 1858, while staying with his aunt's family in Naples, he made the first studies for his early masterpiece The Bellelli Family. He also drew and painted numerous copies of works by Michelangelo, Raphael, Titian, and other Renaissance artists, but—contrary to conventional practice—he usually selected from an altarpiece a detail that had caught his attention: a secondary figure, or a head which he treated as a portrait.
Upon his return to France in 1859, Degas moved into a Paris studio large enough to permit him to begin painting The Bellelli Family—an imposing canvas he intended for exhibition in the Salon, although it remained unfinished until 1867. He also began work on several history paintings: Alexander and Bucephalus and The Daughter of Jephthah in 1859–60; Sémiramis Building Babylon in 1860; and Young Spartans around 1860. In 1861 Degas visited his childhood friend Paul Valpinçon in Normandy, and made the earliest of his many studies of horses. He exhibited at the Salon for the first time in 1865, when the jury accepted his painting Scene of War in the Middle Ages, which attracted little attention. Although he exhibited annually in the Salon during the next five years, he submitted no more history paintings, and his Steeplechase—The Fallen Jockey (Salon of 1866) signaled his growing commitment to contemporary subject matter. The change in his art was influenced primarily by the example of Édouard Manet, whom Degas had met in 1864 (while both were copying the same Velázquez portrait in the Louvre, according to a story that may be apocryphal).
Upon the outbreak of the Franco-Prussian War in 1870, Degas enlisted in the National Guard, where his defense of Paris left him little time for painting. During rifle training his eyesight was found to be defective, and for the rest of his life his eye problems were a constant worry to him.
After the war, Degas began in 1872 an extended stay in New Orleans, Louisiana, where his brother René and a number of other relatives lived. Staying at the home of his Creole uncle, Michel Musson, on Esplanade Avenue, Degas produced a number of works, many depicting family members. One of Degas's New Orleans works, A Cotton Office in New Orleans, garnered favorable attention back in France, and was his only work purchased by a museum (the Pau) during his lifetime.
Degas returned to Paris in 1873 and his father died the following year, whereupon Degas learned that his brother René had amassed enormous business debts. To preserve his family's reputation, Degas sold his house and an art collection he had inherited, and used the money to pay off his brother's debts. Dependent for the first time in his life on sales of his artwork for income, he produced much of his greatest work during the decade beginning in 1874. Disenchanted by now with the Salon, he instead joined a group of young artists who were organizing an independent exhibiting society. The group soon became known as the Impressionists. Between 1874 and 1886 they mounted eight art shows, known as the Impressionist Exhibitions. Degas took a leading role in organizing the exhibitions, and showed his work in all but one of them, despite his persistent conflicts with others in the group. He had little in common with Monet and the other landscape painters in the group, whom he mocked for painting outdoors. Conservative in his social attitudes, he abhorred the scandal created by the exhibitions, as well as the publicity and advertising that his colleagues sought. He also deeply disliked being associated with the term "Impressionist", which the press had coined and popularized, and insisted on including non-Impressionist artists such as Jean-Louis Forain and Jean-François Raffaëlli in the group's exhibitions. The resulting rancor within the group contributed to its disbanding in 1886.
As his financial situation improved through sales of his own work, he was able to indulge his passion for collecting works by artists he admired: old masters such as El Greco and such contemporaries as Manet, Pissarro, Cézanne, Gauguin, Van Gogh, and Édouard Brandon. Three artists he idolized, Ingres, Delacroix, and Daumier, were especially well represented in his collection.
In the late 1880s, Degas also developed a passion for photography. He photographed many of his friends, often by lamplight, as in his double portrait of Renoir and Mallarmé. Other photographs, depicting dancers and nudes, were used for reference in some of Degas's drawings and paintings.
As the years passed, Degas became isolated, due in part to his belief that a painter could have no personal life. The Dreyfus Affair controversy brought his anti-Semitic leanings to the fore and he broke with all his Jewish friends. His argumentative nature was deplored by Renoir, who said of him: "What a creature he was, that Degas! All his friends had to leave him; I was one of the last to go, but even I couldn't stay till the end."
Although he is known to have been working in pastel as late as the end of 1907, and is believed to have continued making sculptures as late as 1910, he apparently ceased working in 1912, when the impending demolition of his longtime residence on the rue Victor Massé forced him to move to quarters on Boulevard de Clichy. He never married and spent the last years of his life, nearly blind, restlessly wandering the streets of Paris before dying in September 1917.