Frank Joseph Guarini (born August 20, 1924) is an American Democratic Party politician, who represented New Jersey in the United States House of Representatives, where he represented the Fourteenth Congressional District for seven terms from 1979 to 1993. He is of Italian descent. Since the death of Al Quie in August 2023, he is the oldest living former representative.^[2]

Guarini graduated from Lincoln High School in 1942. He served in the United States Navy aboard USS Mount McKinley from 1944 to 1946. Guarini received an A.B. from Dartmouth College, in 1947 and a J.D. from New York University School of Law in 1950 as well as an LL.M. in 1955. He pursued graduate work at The Hague Academy of International Law and was admitted to the New Jersey bar in 1951. He commenced practice in Jersey City.

Guarini served in the New Jersey Senate from 1965 to 1972. In 1970, Guarini unsuccessfully challenged incumbent U.S. Senator Harrison A. Williams in the Democratic Primary, losing 66%–34%.^[3]

The Jersey City post office building on the corner of Montgomery and Washington has been dedicated to Guarini. John Cabot University in Rome, Italy, designated its campus as the Frank J. Guarini campus, and the library at New Jersey City University is also named in his honor.

He received the America Award of the Italy-USA Foundation in 2014.

Dartmouth has created the Frank J. Guarini Institute for International Education in recognition of his longtime support of the college.^[4] In 2018, Dartmouth further recognized him by announcing the naming of the Guarini School of Graduate and Advanced Studies in his honor.^[5]

Guarini's alma mater New York University School of Law named two of its centers/institutes after him. The Guarini Center on Environmental, Energy and Land Use Law focuses on land and environmental policy.^[6] The Guarini Institute for Global Legal Studies focuses on transnational law.^[7] After the death of Al Quie in August 2023, he became the oldest living former U.S. Representative.^[8]