William Dwight Whitney (February 9, 1827 – June 7, 1894) was an American linguist, philologist, and lexicographer known for his work on Sanskrit grammar and Vedic philology as well as his influential view of language as a social institution.

He was at first interested in natural sciences, and assisted his older brother Josiah Whitney on a geological survey of the Lake Superior region in 1849, having charge of the botany, the barometrical observations and the accounts.

There, he spent his winters at Berlin studying under Franz Bopp and Albrecht Weber, and his summers were devoted to research under Rudolph von Roth at Tübingen.

He also taught modern languages at the Sheffield Scientific School, and served as secretary to the American Oriental Society from 1857 until he became its president in 1884.

Whitney describes the Ashtadhyayi as "containing the facts of the language cast into the highly artful and difficult form of about four thousand algebraic-like rules (in the statement and arrangement of which brevity alone is had in view at the cost of distinctness and unambiguousness).

This doctrine was borrowed and expanded by Ferdinand de Saussure, and it entered into the posthumous edition of his 'Course', adjusted by his disciples C. Bally and Albert Sechehaye (1916).

The teacher declares: "On the essential point it seems to us that the American linguist is right: language is a convention, and the nature of the sign that is agreed upon remains indifferent."