Lewis Michael Eisenberg is an American financier and diplomat. He earned a B.A. from Dartmouth College in 1964 and an M.B.A. from Cornell University in 1966. He joined Goldman Sachs in 1966, rising to partner in 1976 and co-heading its private equity department. He resigned in 1989 following a civil lawsuit in which he was accused of harassing his former assistant, Kathy Abraham, after she attempted to end a seven-year extramarital affair. After leaving Goldman Sachs, Eisenberg co-founded the private equity firm Granite Capital International Group L.P., with assistance from Dartmouth associates. He has a long history in Republican political fundraising, serving as a GOP finance chairman. He served as Chairman of the Port Authority of New York and New Jersey from 1995 to 2001, during which time the agency operated the World Trade Center and he chaired it through the September 11, 2001, attacks. In 2017, he was confirmed as U.S. Ambassador to Italy and San Marino, serving until 2021.