Brigadier General William O. Darby (February 8, 1911 – April 30, 1945) was a career United States Army officer who fought in World War II, where he was killed in action at age 34 in Italy. He was posthumously promoted to brigadier general. Darby led the famous Darby's Rangers, which evolved into the United States Army Rangers. Darby was subsequently portrayed by James Garner in the 1958 theatrical film about Darby's career titled Darby's Rangers.