Conor Cruise O'Brien (born 1917) is an Irish politician, writer and academic.

Conor Cruise O'Brien was born in Dublin, Ireland in November 1917. He was educated at Sandford Park School and Trinity College Dublin. His college education led to a series of appointments in the public service, most notably in the Department of External Affairs, where he served as a diplomat under Sean MacBride (Nobel Peace Laureate 1974). He was particularly vocal on the anti-partition issue during the 1940s but came to world prominence as a special representative to Dag Hammarskjöld, Secretary General of the United Nations, when, in 1961, Katanga tried to secede from what is now the Democratic Republic of the Congo. Under pressure from a range of international interests, he eventually resigned and wrote 'To Katanga and Back' (1962) which is still considered a classic of both modern African history and the inner workings of the United Nations. From 1962 to 1965 he was Chancellor of the University of Ghana. Following this he was the first Albert Schweitzer Professor of Humanities at New York University until 1969.

Cruise O'Brien returned to Ireland and was elected to Dáil Éireann as a Labour Party candidate. In 1973 he was appointed Minister for Posts & Telegraphs. During this period he developed a hostility to militant Irish republicanism. His views caused controversy within and outside the Government. In 1977 Cruise O'Brien lost his Dáil seat, however he was elected to Seanad Éireann. The following year (1978) he became editor of The Observer newspaper. He held visiting professorships and lectureships throughout the world, particularly in the United States. He coined the acronym GUBU on foot of a statement by Charles Haughey. Up until 1994 he was pro-vice chancellor of the University of Dublin. In 1996 he joined the UK Unionist Party and secured a seat in the elections of May 1996 and was a member of that party's delegation to the peace process talks. He resigned from the party in 1998 after writing an article encouraging unionists to embrace the idea of a United Ireland.

Conor Cruise O'Brien's many books include The Great Melody (1992), his magisterial biography of Edmund Burke (a figure with whom he feels a great personal affinity), and his Memoir: My Life and Themes (1998). He is married to the Irish poet Máire Mhac an tSaoi , daughter of the former Fianna Fáil TD and Tánaiste, Seán MacEntee.