Spence T. Olin (August 20, 1900-April 14, 1995) was an American industrialist and philanthropist. Born in Alton, Illinois, Olin served as an executive of the Olin Corporation, founded in 1892 by his father, Frank W. Olin, to make blasting powder.  He graduated in 1921 from Cornell University with a degree in mechanical engineering. He also received a Doctor of Science from Southern Illinois University in 1958 and a Doctor of Laws from Washington University in 1969.

Olin held a succession of positions in the family enterprises, rising to vice president of an Olin company at the time its Winchester Repeating Arms subsidiary turned out 15 billion rounds of ammunition for the Allies during World War II. He became first vice president when the family holdings were consolidated into Olin Industries after the war, curtailed his day-to-day executive responsibilities after the 1954 Mathieson merger, although he remained a director until 1970.

Olin also devoted much of his life to supporting the Republican Party. An important fund-raiser for Dwight D. Eisenhower, he was national finance chairman for the Republican Party from 1958 to 1960 and treasurer of the National Republican Committee from 1960 to 1962.

As a philanthropist, Olin’s interests were wide ranging. Olin's alma mater, Cornell, and the Washington University School of Medicine in St. Louis were leading beneficiaries.