Lieutenant-Colonel William Ledyard (December 6, 1738 – September 6, 1781) was an American military officer who served in the Connecticut Militia in the Revolutionary War.

During the conflict, he commanded Fort Griswold in Groton, Connecticut, which was attacked by British forces led by Benedict Arnold.

"According to the generally received tradition, Bromfield immediately plunged the weapon to the hilt in the body of Ledyard, killing him instantly.

Arnold wrote the following account of the battle in a dispatch to Henry Clinton two days afterward: "I have inclosed a return of the killed and wounded, by which your excellency will observe that our loss, though very considerable, is short of the enemy's, who lost most of their officers, among whom was their commander, Col. Ledyard.

The events of Fort Griswold and the subsequent death of Ledyard was depicted in Turn: Washington's Spies Season 4, Episode 10.