Henri René Albert Guy de Maupassant (UK: /ˈmoʊpæsɒ̃/, US: /ˈmoʊpəsɒnt, ˌmoʊpəˈsɒ̃/; French: [ɡi d(ə) mopasɑ̃]; 5 August 1850 – 6 July 1893) was a 19th-century French author, celebrated as a master of the short story, as well as a representative of the naturalist school, depicting human lives, destinies and social forces in disillusioned and often pessimistic terms.

Maupassant was a protégé of Gustave Flaubert and his stories are characterized by economy of style and efficient, seemingly effortless dénouements. Many are set during the Franco-Prussian War of the 1870s, describing the futility of war and the innocent civilians who, caught up in events beyond their control, are permanently changed by their experiences. He wrote 300 short stories, six novels, three travel books, and one volume of verse. His first published story, "Boule de Suif" ("The Dumpling", 1880), is often considered his most famous work.

Henri-René-Albert-Guy de Maupassant was born on 5 August 1850 at the late 16th-century Château de Miromesnil (near Dieppe in the Seine-Inférieure (now Seine-Maritime) Department, France), the elder son of Gustave de Maupassant (1821–99) and Laure Le Poittevin, whose family hailed from the prosperous bourgeoisie. His mother urged her husband when they married in 1846 to obtain the right to use the particule or form "de Maupassant" instead of "Maupassant" as his family name, in order to indicate noble birth. Gustave's great-great-grandfather, Jean-Baptiste de Maupassant (1699–1774), conseiller-secrétaire to King Louis XV, had been ennobled by Emperor Francis I in 1752, and although his family were considered petite noblesse they had not yet received official recognition by the Kingdom of France. He then obtained from the Tribunal Civil of Rouen by royal decree dated 9 July 1846 the right to style himself "de Maupassant" instead of "Maupassant", being formally assumed as the family name before the birth of his children.

When Maupassant was 11 and his brother Hervé was five, his mother, an independent-minded woman, risked social disgrace to obtain a legal separation from her husband, who was violent towards her.

After the separation, Laure Le Poittevin kept custody of her two sons. In the absence of Maupassant's father, his mother became the most influential figure in the young boy's life. She was an exceptionally well-read woman and was very fond of classical literature, particularly Shakespeare. Until the age of thirteen, Guy lived happily with his mother, at Étretat in Normandy. At the Villa des Verguies, between the sea and the luxuriant countryside, he grew very fond of fishing and of outdoor activities. When Guy reached the age of thirteen, his mother placed her two sons as day boarders in a private school, the Institution Leroy-Petit, in Rouen—the Institution Robineau of Maupassant's story La Question du Latin—for classical studies. From his early education, he retained a marked hostility to religion, and to judge from verses composed around this time, he deplored the ecclesiastical atmosphere, its ritual and discipline. Finding the place unbearable, he finally got himself expelled in his penultimate year.

In 1867, while he was in junior high school, Maupassant met Gustave Flaubert at Croisset on the insistence of his mother. Next year, in autumn, he was sent to the Lycée Pierre-Corneille in Rouen where he proved a good scholar, indulging in poetry and taking a prominent part in theatricals. In October 1868, at the age of 18, he saved the famous poet Algernon Swinburne from drowning off the coast of Étretat.

The Franco-Prussian War broke out soon after his graduation from college in 1870 and Maupassant volunteered to serve in the French Army without attending military academy as aspirant. In 1871, he left Normandy and moved to Paris, where he spent ten years as a clerk in the Navy Department. During this time his only recreation and relaxation was boating on the Seine on Sundays and holidays.

Gustave Flaubert took him under his protection and acted as a kind of literary guardian to him, guiding his debut in journalism and literature. At Flaubert's home he met Émile Zola (1840–1902) and the Russian novelist Ivan Turgenev (1818–1883), as well as many of the proponents of the realist and naturalist schools. He wrote and himself played (1875) in a comedy - "À la feuille de rose, maison turque" - with Flaubert's blessing.