William L. Thornton (November 28, 1844 – December 29, 1915) was an American lawyer and politician from New York.

The family removed to Monticello, Sullivan County, New York when William was still a child.

His defeated Democratic opponent Timothy Bush claimed that the offer to serve for a reduced salary was a bribe to the people, and Thornton should thus be declared ineligible under the anti-bribery law.

This view was accepted by Supreme Court Justice Osborne, who declared the office vacant.

He died on December 29, 1915, in front of his home in Monticello, New York, from "heart disease" or "apoplexy";[4] and was buried at the Rock Ridge Cemetery there.