Ernest Lou Medina (born August 27, 1936) is a former captain of infantry in the United States Army. He served during the Vietnam War and was acquitted in a court-martial of war crimes charges in 1971. He was the commanding officer of Company C, 1st Battalion, 20th Infantry of the 11th Brigade, Americal Division, the unit responsible for the My Lai Massacre of 16 March 1968.