William Thomas Cahill (June 25, 1912 – July 1, 1996) was an American Republican Party politician who served as the 46th Governor of New Jersey, from 1970 to 1974, and who represented New Jersey's 1st congressional district in the U.S. House of Representatives from 1959 to 1967 and the state's 6th district from 1967 to 1970.
Though born in Philadelphia, Pennsylvania, Cahill moved to New Jersey with his parents in 1919. He attended Camden Catholic High School in Camden, New Jersey, and graduated in 1929. Afterwards, Cahill graduated St. Joseph's College (now Saint Joseph's University) at Philadelphia in 1933. He returned to Camden to study at the Rutgers School of Law - Camden, receiving his law degree in 1937.
In 1937 and 1938, Cahill was a special agent of the Federal Bureau of Investigation. In 1939 he was admitted to the bar and began his political career. Living in Collingswood, New Jersey, Cahill was the city prosecutor of Camden, New Jersey in 1944 and 1945, was the first assistant prosecutor of Camden County from 1948-1951 and was a special deputy attorney general of the State of New Jersey in 1951. Cahill was a member of the New Jersey General Assembly from 1951-1953.
Cahill was elected to the Eighty-sixth and to the five succeeding Congresses until his resignation from his congressional seat to assume his seat as Governor, serving in office from January 3, 1959 to January 19, 1970.
Cahill served as Governor of New Jersey from January 20, 1970 - January 15, 1974, not being able to run for a second term after he was defeated in the primary election that June. After his term as governor, Cahill was a senior fellow at the Woodrow Wilson School of Public and International Affairs at Princeton University from 1974-1978. While governor, Cahill named his predecessor, Richard J. Hughes as chief justice of the New Jersey Supreme Court.
He died in Haddonfield, New Jersey and is interred at Calvary Cemetery in Cherry Hill Township, New Jersey.