James Smithson, F.R.S., M.A. (1764 – 27 June 1829) was a British mineralogist and chemist noted for having left a bequest in his will to the United States of America, to create "an establishment for the increase and diffusion of knowledge among men" to be called the Smithsonian Institution.
Not much is known about Smithson's life: his scientific collections, notebooks, diaries, and correspondence were lost in a fire that destroyed the Smithsonian Institution Building in 1865; only the 213 volumes of his personal library and some personal writings survived. Smithson was born Jacques Louis Macie on an unknown date early in 1764, in Paris, France, an illegitimate, unacknowledged son of an English landowner, the highly regarded and accomplished Sir Hugh Smithson, 4th Baronet of Stanwick, north Yorkshire, who had married into the Percy family. In 1766 he became 1st Duke of Northumberland, K.G.
James Smithson's mother was his father's mistress, Elizabeth Hungerford Keate, the daughter of John Keate, an uncle of George Keate (1729–1797) who was elected to the Royal Society in 1766. Elizabeth was an heiress of the Hungerfords of Studley. She was also the widow of John Macie, of Weston, near Bath, Somerset; so the young Smithson originally was called Jacques Louis Macie. His mother later married John Marshe Dickinson, a troubled son of Marshe Dickinson who was Lord Mayor of the City of London in 1757 and Member of Parliament. During this marriage, she had another son; but the 1st Duke of Northumberland, rather than Dickinson, is thought to have been the father of this second son also.