Robert Dean Blackwill (born August 8, 1939) is a retired American diplomat, author, senior fellow at the Council of Foreign Relations, and lobbyist. Blackwill served as the United States Ambassador to India under President George W. Bush from 2001 to 2003 and as United States National Security Council Deputy for Iraq from 2003 to 2004, where he was a liaison between Paul Bremer and Condoleezza Rice.

Blackwill was born on August 8, 1939, in Kellogg, Idaho and grew up in Kansas. In June 2001, at a Senate confirmation hearings to become ambassador to India, he said, "From my boyhood on the Great Plains, I brought back east more than 30 years ago the values of Kansas and its people: honesty, candor, compassion, hard work, a dogged stamina in the face of challenge and adversity, a sense of humor, a recognition of one's own limitations, and a deep and abiding love of country." He earned a B.A. from Wichita State University.

Blackwill served as a Peace Corps volunteer in Malawi from 1964 to 1966. While in the Peace Corps, he served with writer Paul Theroux, who Blackwill later described as "the glorious American writer who was my friend in the Peace Corps in Africa more than thirty years ago". In an interview with Rediff News on June 27, 2006, Blackwill was asked if he was still in contact with Theroux, and he replied, "Not recently. But I just finished reading his new novel, Blinding Light. It is terrific."

In 1967, Blackwill was appointed as a Foreign Service Officer. He served as a training officer in the Bureau of Personnel of the US State Department from 1968 to 1969 and as an associate watch officer in the State Department's Operations Center from 1969 to 1970.

Blackwill took Swahili language training in 1970 at the Foreign Service Institute. He served as a political officer in Nairobi, Kenya from 1970 to 1972 and as a staff officer in the Executive Secretariat of the State Department from 1972 to 1973. In 1974, Blackwill was a special assistant to State Department counselor Helmut Sonnenfeldt. While he was a special assistant, Blackwill worked closely with Paul Bremer, who was then a chief aide to Secretary of State Henry Kissinger. Blackwill and Bremer forged a close relationship through mediating policy differences between their bosses. The two would come to work together again thirty years later in August 2003, when Bremer was named by President George W. Bush to lead the Coalition Provisional Authority in Iraq and Blackwill was named to the National Security Council staff to coordinate between Washington, D.C., and Baghdad. From 1975 to 1978, Blackwill served as a political-military officer in London, England. He served as political counselor in Tel Aviv, Israel from 1978 to 1979. Blackwill became the Director of Western European Affairs on the National Security Council staff at the White House in 1979.

Blackwill served as the principal deputy assistant secretary for political-military affairs in the State Department in 1981. Blackwill served as principal deputy assistant secretary for European affairs from 1982 to 1983. After his return from a two-year sabbatical at Harvard University, President Ronald Reagan nominated him to Senior Foreign Service, Class of Minister-Counselor on March 29, 1985, and designated him to be the chief negotiator of the US with the Warsaw Pact for the Mutual and Balanced Force Reductions talks. Blackwill served in this position with the rank of ambassador. On March 13, 1989, President George H. W. Bush appointed Blackwill as special assistant to the president for national security affairs and as senior director for European and Soviet affairs.

From 1983 to 1985, Blackwill took a sabbatical from the State Department and served as associate dean and faculty member at the John F. Kennedy School of Government at Harvard University.

After two years as representative to the Mutual and Balanced Force Reductions Negotiations, Blackwill rejoined the Harvard faculty in 1987. There, he served the Kennedy School as associate dean and the Belfer Lecturer in International Security for fourteen years until 2001. During his tenure, Blackwill taught foreign and defense policy and public policy analysis. He was also faculty chair for executive training programs for business and government leaders from Saudi Arabia, Kuwait, the Palestinian Authority, and Kazakhstan, as well as military General Officers from Russia and the People's Republic of China.