William Byrd III (September 6, 1728 – January 1 or January 2, 1777) was the son of William Byrd II and the grandson of William Byrd I. He inherited his family's estate of approximately 179,000 acres of land in Virginia and continued their planter prestige as a member of the Virginia House of Burgesses. He chose to fight in the French and Indian War rather than spend much time in Richmond. In 1756 he was colonel of the Second Virginia Regiment. Despondent and broke, Byrd III committed suicide on January 1 or 2, 1777. He was buried in the cemetery at the old Westover Church.