Wendell Fertig (December 16, 1900 – March 24, 1975) was an American civil engineer, in the American-administered Commonwealth of the Philippines, who organized and commanded an American-Filipino guerrilla force on the Japanese-occupied, southern Philippine island of Mindanao during World War II. Fertig's widely scattered guerrilla force numbered approximately 32,000. He faced about 50,000 Japanese soldiers, mostly garrison troops in towns and cities.