Matthew Nimetz (/ˈnɪmɪts/; born June 17, 1939) is an American diplomat and a former lawyer and retired managing director of a global private equity firm.

[3] He served as law clerk to Supreme Court Justice John Marshall Harlan II from 1965 to 1967, before serving as a staff assistant to President Lyndon B. Johnson until 1969,[3] where he worked on the domestic policy staff under Joseph A. Califano Jr. At the White House he worked on many of the Great Society programs relating to civil rights, crime, housing, environmental and conservation issues, and other related programs.

He was liaison with various government departments relating to domestic violence following the assassination of Martin Luther King Jr. and during the Poor People's Campaign in Washington, D.C. in 1968.

Following his stay at the White House, he worked with the New York City law firm Simpson Thacher & Bartlett as an associate from 1969 to 1973 and as a partner from 1974 to 1977.

These included sales of military weapons and related material to other countries, and such other areas such as scientific and technical cooperation, nuclear nonproliferation issues, environmental matters, and the US Government's international communications activities.

[8] The major issues between the two neighbors were not, however, resolved in the Interim Agreement, and in 1999, Nimetz was appointed to succeed Cyrus Vance as the personal envoy of the UN secretary-general regarding the naming dispute.

[9] Nimetz believed that the long-running issue was capable of resolution and made a number of proposals to the two parties during the course of his mediation efforts to bring them closer to a solution.

During intense efforts commencing with his proposal of January 11, 2018, the parties hammered out an agreement, negotiated primarily by the two foreign ministers, Nikola Dimitrov for North Macedonia and Nikos Kotzias of Greece, and ultimately by the two prime ministers Alexis Tsipras of Greece and Zoran Zaev of North Macedonia, with the intensive mediation support of Nimetz and his UN team.

[13] As of 2014[update], he was a director/founding (former) chair of the Centre for Democracy and Reconciliation in Southeastern Europe, Thessaloniki, Greece;[14] a trustee emeritus of the Rubin Museum of Art, New York;[15] a former director and co-chair of Green City Force, Brooklyn, New York;[16] a trustee emeritus of National Committee on American Foreign Policy.