Augustus Saint-Gaudens (/ˌseɪntˈɡɔːdənz/; March 1, 1848 – August 3, 1907) was an Irish sculptor of the Beaux-Arts generation who embodied the ideals of the American Renaissance. Saint-Gaudens was born in Dublin to an Irish-French family, and raised in New York City. He traveled to Europe for further training and artistic study. After he returned to New York City, he achieved major critical success for his monuments commemorating heroes of the American Civil War, many of which still stand. Saint-Gaudens created works such as the Robert Gould Shaw Memorial on Boston Common, Abraham Lincoln: The Man, and grand equestrian monuments to Civil War generals: General John Logan Memorial in Chicago's Grant Park and William Tecumseh Sherman at the corner of New York's Central Park. In addition, he created the popular historicist representation of The Puritan.

Saint-Gaudens also created Classical works such as the Diana, and employed his design skills in numismatics. He designed the $20 Saint Gaudens Double Eagle gold coin (1905–1907) for the US Mint, considered one of the most beautiful American coins ever issued, and the $10 "Indian Head" gold eagle; both of these were minted from 1907 until 1933. In his later years he founded the "Cornish Colony", an artist's colony in New Hampshire that included notable painters, sculptors, writers, and architects. His brother Louis Saint-Gaudens, with whom he occasionally collaborated, was also a well-known sculptor.

Saint-Gaudens was born in Dublin, Ireland, to an Irish mother and French father, Bernard Paul Ernest Saint-Gaudens, a shoemaker by trade from a village in the French Pyrenees, Aspet, 15 kilometers from Saint-Gaudens. His parents emigrated to America when he was six months of age, and he was reared in New York City.

In 1861, he became an apprentice to a cameo-cutter, Louis Avet, and took evening art classes at the Cooper Union in New York City. Two years later, he was hired as an apprentice of Jules Le Brethon, another cameo cutter, and enrolled at the National Academy of Design. His apprenticeship was completed by the age of 19 and he traveled to Paris in 1867, where he studied in the atelier of François Jouffroy at the École des Beaux-Arts.

In 1870, he left Paris for Rome to study art and architecture, and worked on his first commissions. There he met a deaf American art student, Augusta Fisher Homer. They married on June 1, 1877. The couple had one child, a son named Homer Saint-Gaudens.

In 1874, Edwards Pierrepont, a prominent New York reformer, hired Saint-Gaudens to create a marble bust of himself. Pierrepont, a phrenologist, proved to be a demanding client, insisting that Saint-Gaudens make his head larger. Saint-Gaudens said that Pierrepont's bust "seemed to be affected with some dreadful swelling disease" and he later told a friend that he would "give anything to get hold of that bust and smash it to atoms".

In 1876, he won a commission for a bronze David Farragut Memorial. He rented a studio at 49 rue Notre Dame des Champs. Stanford White designed the pedestal. It was unveiled on May 25, 1881, in Madison Square Park. He collaborated with Stanford White again in 1892–1894 when he created Diana as a weather vane for the second Madison Square Garden building in New York City; a second version used is now in the collection of the Philadelphia Museum of Art, with several reduced versions in museums including the Metropolitan Museum of Art in New York City. The statue stood on a 300-foot-high tower, making Diana the highest point in the city. It was also the first statue in that part of Manhattan to be lit at night by electricity. The statue and its tower was a landmark until 1925 when the building was demolished.

In New York, he was a member of the Tile Club, a group of prominent artists and writers, including Winslow Homer (his wife's fourth cousin), William Merritt Chase and Arthur Quartley. He was also a member of The Lambs, Salmagundi Club and the National Arts Club in New York City.