William du Pont (1855-1928) was an industrialist and member of the promienent du Pont family of Delaware, whose family business was the E.I. du Pont de Nemours & Company, also known as the DuPont Company which was a large manufacturer of gunpowder. He was the youngest son of Louisa Gerhard du Pont (1816-1900) and General Henry du Pont (1812-1889), who was the third president of the DuPont Company. From 1869 to 1872, William du Pont attended the Lake Mohegan boarding school in New York State, and in 1872, he was admitted to the Massachusetts Institute of Technology (MIT). However, he left MIT at the beginning of the 1873 spring semester due to medical problems with his eye.

William du Pont became involved in the family business in 1876. As an assistant to his father, DuPont Company president Henry du Pont, he managed the company's farms, developing skills instrumental in his future activities in horse and cattle breeding. His work in explosives manufacturing began in 1880, when he was appointed to help his cousin Lammot du Pont (1831-1884) in the first du Pont high explosives (dynamite) enterprise, Repauno Chemical Company. At first, William du Pont was the company's secretary and treasurer (1880-1884); then, after Lammot du Pont's tragic death on March 29, 1884, he became president from 1884 to 1892. At the same time, he performed treasurer and presidential duties for the Hercules Powder Company and the Torpedo Company, which were also associated with Lammot du Pont.

After his father died in 1889, he gave up his partnership in the DuPont Company and resigned from Repauno, Hercules and the Torpedo companies. In 1914, he returned for a short period of time to active duty as the director and the chairman of the Financial Committee of the E.I. du Pont de Nemours Powder Company. However, in March 1916, together with his cousin Alfred I. du Pont (1864-1935), he was expelled from the committee and the board due to their conflict with the company's new president, his coutsin Pierre S. du Pont (1870-1954). William du Pont's last involvement with the explosives industry was his investment and directorship, from 1919 through 1926, in the U.S. Flashless Powder Company (a.k.a. U.S.F. Powder Company), a company organized by his cousins Francis I. du Pont (1873-1942) and Ernest du Pont (1880-1944) to develop and manufacture powder for night gunfire.

In 1916, William du Pont, together with his cousin Alfred I. du Pont, bought the Delaware Trust Company. He remained affiliated with it for the next twelve years as its vice president (1916-1920), president (1920-1922), and chairman of the board (1923-1928). From 1917, he was on the board of directors of the United States Fidelity and Guarantee Company of Baltimore, also. His previous involvement in the banking business included service on the board of directors and on the Executive Committee of the Equitable Guarantee & Trust Company of Wilmington, Delaware in the late 1880s through the early 1890s.

As for his personal life, in 1878, William du Pont married his cousin May Lammot du Pont (1854-1927), the daughter of Victor du Pont (1828-1888) and Alice Hounsfield du Pont (1833-1904). The couple divorced in 1892 in South Dakota. He spent six month in that state in order to have residency for the divorce. In June 1892, he married Annie Rogers Zinn (1858-1927), the daughter of the locomotive maker Theodore Rogers (1829-1871) and Mary Andrews Rogers (1836-1918). Annie Rogers Zinn was the divorced wife of George Zinn (1842-1899) of New Castle, Delaware. William and Annie du Pont, alienated by the du Pont family and Wilmington society, left the United States and settled in Europe for ten years. The couple had two children: a daughter, Marion du Pont Somerville Scott (1894-1983) and a son, William du Pont Jr. (1896-1965), and supported a son from her previous marriage, George Zinn (1883-1929). While living in England, the family maintained their home at "Bellevue Hall" near Wilmington, and in 1900, purchased a home in Virginia named "Montpelier," formerly owned by the fourth President of the United States, James Madison. The family moved there in the beginning of 1902.

du Pont was affiliated through founding and board positions in the banking and railroad industry. He played a significant role in the American horse and cattle breeding industry. He performed judging duties at numerous horse shows around the country and financed prizes and awards. Also, he was a member of various hunting, yachting, and social clubs. As a member of the American Game Protective and Propagation Association, William du Pont worked in support of the Migratory Bird Treaty Act of 1918.

William du Pont died on January 20, 1928, at his estate Altama, near Brunswick, Georgia. His wife, Annie Rogers du Pont, had died in London a year earlier on January 22, 1927.