Karl Schmolsmire Day (May 30, 1896 - January 19, 1973) was a highly decorated naval aviator of the United States Marine Corps Reserve with the rank of Lieutenant General.
A veteran World War I, Day served with Northern Bombing Group on the Belgian front and received Navy Cross, the United States military's second-highest decoration awarded for valor in combat.
He then resigned his commission and worked in various civilian jobs until the beginning of World War II.
Day was subsequently recalled to active duty and served as Air Base Commander during the Battle of Peleliu in September 1944.