James Mercer (February 26, 1736 – October 31, 1793), also known as William James Mercer, was born in Virginia at Malborough plantation on February 26, 1736. He was the son of John Mercer and Catherine Mason Mercer. He graduated from the College of William and Mary about 1755.
He served as a captain in the French and Indian War and was commander of Fort Loudoun in Winchester, Virginia, in 1756.
and became a member of the House of Burgesses in 1765. In 1774, he was a member of the general assembly. He was an American lawyer and jurist who served as a delegate for Virginia to the Continental Congress in 1779.
He was appointed a judge of the general court in 1780 and became a judge on the first Court of Appeals as a result. In 1789, he was appointed as a member of the reorganized Court of Appeals. He remained on the bench of that court until his death in Richmond on October 31, 1793.
Mercer was the brother of George Mercer and John Francis Mercer, and father of Charles Fenton Mercer.