Herbert Smith Duffy (February 25, 1900 – February 29, 1956) was Ohio Attorney General from 1937 to 1939 and from 1949 to 1951. Duffy, a Democrat from Columbus, Ohio, settled a case against the Ohio Bell Telephone Company. The case was before the Public Utilities Commission of Ohio, the Ohio Supreme Court and the United States Supreme Court, and lasted fourteen years. Duffy wrote a biography of former President William Howard Taft, which was published in 1930. He was national commander of the American Legion at the Inter-Allied War Veterans' Congress in Brussels, Belgium in 1935.