Daniel Patrick Moynihan (March 16, 1927 – March 26, 2003) was an American politician and diplomat. A member of the Democratic Party, he represented New York in the United States Senate from 1977 until 2001 and served as an adviser to President Richard Nixon.

Born in Tulsa, Oklahoma, Moynihan moved at a young age to New York City. Following a stint in the navy, he earned a Ph.D. in history from Tufts University. He worked on the staff of New York Governor W. Averell Harriman before joining President John F. Kennedy's administration in 1961. He served as an Assistant Secretary of Labor under Presidents Kennedy and President Lyndon B. Johnson, devoting much of his time to the War on Poverty. In 1965, he published the controversial Moynihan Report. Moynihan left the Johnson administration in 1965 and became a professor at Harvard University.

In 1969, he accepted Nixon's offer to serve as an Assistant to the President for Domestic Policy, and he was elevated to the position of Counselor to the President later that year. He left the administration at the end of 1970, and accepted appointment as United States Ambassador to India in 1973. He accepted President Gerald Ford's appointment to the position of United States Ambassador to the United Nations in 1975, holding that position until early 1976; later that year he won election to the Senate.

Moynihan served as Chairman of the Senate Environment Committee from 1992 to 1993 and as Chairman of the Senate Finance Committee from 1993 to 1995. He also led the Moynihan Secrecy Commission, which studied the regulation of classified information. He emerged as a strong critic of President Ronald Reagan's foreign policy and opposed President Bill Clinton's health care plan. He frequently broke with liberal positions, but opposed welfare reform in the 1990s. He also voted against the Defense of Marriage Act, the North American Free Trade Agreement, and the Congressional authorization for the Gulf War. He was tied with Jacob K. Javits as the longest-serving Senator from the state of New York until they were both surpassed by Chuck Schumer in 2023.