William Mercer Lennox (August 8, 1900 – October 7, 1991) was a Democratic politician from Philadelphia who served as sheriff from 1952 to 1972.

Born in Philadelphia on August 8, 1900, William M. Lennox was a son of Robert Lennox and his wife, Theresa Howarth Lennox.^[1] At the age of seventeen, he enlisted in the United States Navy and served in the First World War.^[2]

After the war, he worked as the business manager of athletics at the University of Pennsylvania.^[3] In 1928, Lennox married Kathryn Kilgallen, with whom he had five children, Nancy, William, Jane, Mary Ellen and Benedict.^[2]

In 1950, Democratic ward leaders nominated Lennox for the Philadelphia City Council during a special election that followed the death of Charles E. O'Halloran.^[2] He won and served the remained of the term, which ended in 1952.^[3] In 1951, instead of running for another term on the council, Lennox ran for sheriff and won.^[3] He was reelected in 1955, 1959, 1963, and 1967.^[3]

After his fifth term, Lennox retired from office at the age of seventy-one, but remained active in the community, working as a volunteer at St. John's Hospice in Center City.^[3]

Lennox died on October 7, 1991.^[3]

• List of members of Philadelphia City Council from 1920 to 1952
• 1980 interview with Lennox