Cyrus Roberts Vance (March 27, 1917–January 12, 2002), was the United States Secretary of State under President Jimmy Carter from 1977 to 1980. He approached foreign policy with an emphasis on negotiation over conflict and a special interest in arms reduction. In April of 1980, Vance resigned in protest of a secret mission to rescue American hostages in Iran.

Vance received a bachelors degree from Yale, where he was a member of the secret society, Scroll and Key. After graduating from Yale Law School in 1942, Vance served in the Navy until 1946 and then worked in a New York City law firm before entering the government. As Deputy Secretary of Defense under President Lyndon Johnson, he at first supported the Vietnam War but changed his views by the late 1960s, advising the president to pull out of North Vietnam. In 1968 he served as a delegate to peace talks in Paris.

As Secretary of State in the Carter administration, Vance pushed for negotiations and economic ties with the Soviet Union and clashed frequently with the more hawkish National Security Advisor Zbigniew Brzezinski, who tended to see the world in bipolar terms. Vance tried to advance arms limitations by working on the SALT II agreement with Russia, which he saw as the central diplomatic issue of the time. He was heavily instrumental in Carter's decision to return the Canal Zone to Panama and in the Camp David Accords agreement between Israel and Egypt.

After the Accords, Vance's influence in the administration began to wane as Brzezinski's rose. His role in talks with People's Republic of China was marginalized and his advice for a response to the Shah of Iran's collapsing regime was ignored. Shortly thereafter, when fifty-three American hostages were held in Iran, he worked actively in negotiatons but to no avail. Finally, when Carter ordered a secret military rescue, Vance resigned in opposition. The rescue attempt failed.

Vance returned to his law practice in 1980, but was repeatedly called back to public service throughout the 1980s and 1990s, participating in diplomatic missions to Bosnia, Croatia, and South Africa.

Vance also was a member of the Trilateral Commission.