Paul Efthemios Tsongas (February 14, 1941 – January 18, 1997) was an American politician who represented Massachusetts in the United States Senate from 1979 until 1985 and in the United States House of Representatives from 1975 until 1979. A member of the Democratic Party, he ran for president in 1992. He won eight contests during the presidential primaries but ultimately lost the nomination to Bill Clinton, who later won the general election.

Born in Lowell, Massachusetts, Tsongas graduated from Dartmouth College, Yale Law School and the Kennedy School of Government. After working for the Peace Corps and as an aide to Congressman F. Bradford Morse, Tsongas successively won election as a city councilor and county commissioner. In 1974, Tsongas was elected to the House of Representatives representing Massachusetts's 5th congressional district, after defeating incumbent Paul W. Cronin. In 1978, he ran for Senate, and defeated incumbent Republican Edward Brooke.

In Congress, Tsongas established a reputation as a social liberal and fiscal conservative. Tsongas was diagnosed with non-Hodgkin lymphoma in 1983 and declined to seek re-election in 1984. He returned to politics after undergoing a successful bone marrow transplant. He experienced early success in the 1992 Democratic presidential primaries, winning the New Hampshire primary, but withdrew from the race in March 1992 and endorsed Clinton. An opponent of deficit spending, Tsongas co-founded the Concord Coalition. He died in 1997 of complications from pneumonia and non-Hodgkin lymphoma.