John Francis Mercer (May 17, 1759 – August 30, 1821) was a Founding Father of the United States, politician, lawyer, planter, and slave owner from Virginia and Maryland.

An officer during the Revolutionary War, Mercer initially served in the Virginia House of Delegates and then the Maryland State Assembly.

[1][2] Mercer was born in 1759 at Marlborough plantation in Stafford County in the Colony of Virginia, to prominent lawyer, planter and investor in western lands John Mercer (1704–1768) and his second wife, the former Ann Roy (1729–1770), the daughter of Dr. Mungo Roy of Essex County, Virginia.

His namesake half-brother, Captain John Fenton Mercer (1735–1756) had been killed and scalped in western Virginia during the French and Indian War.

[3] Like all his brothers who lived to adulthood, Mercer attended the College of William and Mary, graduated in 1775 and read law with Thomas Jefferson.

[4] During the American Revolutionary War, Mercer accepted a commission as lieutenant in the 3rd Virginia Regiment in the Continental Army.

After General Cornwallis' surrender in 1781, Stafford County voters elected Mercer as one of their two representatives in the Virginia House of Delegates in 1782, where he served alongside Charles Carter.

[7] In 1785 Mercer married his wife, as discussed below, and soon moved to Anne Arundel County, Maryland, where he operated her estates ("West River Farm") using enslaved labor.

[16] His nephew, congressman Charles Fenton Mercer, opposed slavery and was president of the American Colonization Society.