Joseph S. Frelinghuysen (March 12, 1869-February 8, 1948) represented New Jersey as a Republican in the United States Senate from 1917 to 1923.
Born in Raritan, New Jersey into a historic New Jersey political family, Joseph Frelinghuysen was the nephew of Frederick T. Frelinghuysen and cousin of current congressman Rodney Frelinghuysen.
After fighting in the Spanish-American War and starting an insurance business, Frelinghuysen was elected to the state Senate in 1905 and became president of that body in 1909. He held several state-wide offices before being elected to the U.S. Senate in 1916. He was New Jersey's first directly elected senator following ratification of the 17th Amendment to the Constitution in 1913.
After a failed reelection bid in 1922, Frelinghuysen returned to the insurance business. He died in 1948 in Tucson, Arizona. He is interred at St. Bernard's Cemetery in Bernardsville, New Jersey.