William Lounsbery (December 25, 1831 – November 8, 1905) was an American lawyer, Civil War veteran, and politician who served one term as a U.S. Representative from New York from 1879 to 1881.

Born at Stone Ridge, New York, he was the son of John (1803-1864) and Sarah Peters Lounsbery (1796-1866).

He was a descendant of New Paltz founder and Huguenot Louis DuBois and the Hasbrouck family.

During the Civil War was commissary of the Twentieth Regiment, New York Militia, with the rank of first lieutenant, during its three months' service.

This article incorporates public domain material from the Biographical Directory of the United States Congress