The 1946 United States Senate election in Massachusetts was held on November 5, 1946. Incumbent Democratic Senator David I. Walsh ran for re-election to a fifth term in office, but was defeated by Republican former Senator Henry Cabot Lodge Jr., who returned from service in World War II.

David Ignatius Walsh was an American politician from Massachusetts. A member of the Democratic Party, he served as the state's 46th governor before winning election to several terms in the United States Senate, becoming the first Irish Catholic from Massachusetts to fill either office.