William Pierce (c. 1740 – December 10, 1789) was an army officer during the American Revolutionary War and a member of the United States Constitutional Convention of 1787. Little is known about Pierce's early life or background. He was born in York County, Virginia in 1753. He served in the Continental Army through most of the War of Independence. He was commissioned a captain in the 1st Continental Artillery Regiment on November 30, 1776. Due to failing health, he left the artillery to serve as an aide-de-camp to General John Sullivan during Sullivan's expedition against the Iroquois in 1779.