William Thornton (May 20, 1759 - 28 March, 1828) was the original architect of the United States Capitol. Born on Jost Van Dyke in the British Virgin Islands, Thornton received medical training in Edinburgh, Scotland. He emigrated to the United States of America in 1787.

Thornton's design for the Capitol had been submitted after the close of a competition in which 17 entries were found wanting. His plan was approved on July 25, 1793, with the award of $500 and a city lot in Washington, D.C..

Other notable designs by Thornton were the Library Company in Philadelphia, Pennsylvania and the Tayloe house or Octagon House in Washington, D.C., once headquarters of the American Institute of Architects.

Thornton was also the first Superintendent of the United States Patent Office from June 1, 1802 until his death in 1828.

William E. Thornton is also a now retired American astronaut