William Matthew Ketchum (born September 2, 1921) was a Republican member of the United States House of Representatives from California. He represented California’s 18th congressional district and served three terms in Congress. His tenure in the U.S. House began on January 3, 1973, and concluded on January 3, 1979.

During his time in office, Ketchum served as a representative for California at the federal level, participating in the legislative work of the House as a member of the Republican Party. Identified in congressional records by the biographical guide ID K000153, he was part of the delegation that represented California in the 1970s. William Matthew Ketchum left office as a former member of Congress after his third term ended in 1979.