William Marshall Bullitt (March 4, 1873 – October 3, 1957) was an influential lawyer and author who served as Solicitor General of the United States (1912–1913).

His ancestors arrived in Kentucky in the 1700s: the Bullitts, the Walkers, the Christians (relatives of Patrick Henry) and the Logans (descended from United States Supreme Court Chief Justice John Marshall).

During his service (1912–1913), Bullitt argued cases involving enforcement of the Sherman Anti-Trust Act on cotton corners, and publicity laws and mail rates regarding newspapers and their circulation.

In 1933, Bullitt joined the trustees of the Carnegie Endowment for International Peace after being nominated by his successor as solicitor general, John W. Davis.

During late November and early December 1948, he wrote a "Factual Review of the Whittaker Chambers-Alger Hiss Controversy," which he soon after had published.

Following a discussion with his friend G. H. Hardy, Bullitt set out to obtain first-edition works by what he considered the twenty-five greatest mathematicians of all time.

Among the texts in the collection are works by Albert Einstein, Isaac Newton, René Descartes, Galileo, Copernicus, Euclid, Carl Friedrich Gauss, Leonhard Euler, and Gottfried Leibniz.