吴丹于1961年至1971年任联合国秘书长。他是在达格•哈马舍尔德秘书长于1961年9月坠机殉难后被推选为这个世界组织的首长。

吴丹于1909年1月22日出生于缅甸的班达诺，在班达诺的国立中学和仰光的大学学院受教育。

吴丹在进入外交界之前，曾经担任教育和新闻方面的工作。他担任过母校班达诺国立中学的高中教员，并于获得英语一本地话中学教师资格考试第一名之后，在1931年升任校长。

在第二次世界大战以前，他曾任缅甸教科书委员会和国家教育委员会的委员及中小校长联合会执行委员会委员。此外，他还是很活跃的一名自由采访记者。

1942年，吴丹担任几个月的缅甸教育改组委员会秘书。翌年，他回国立中学再担任了四年校长。

1947年，吴丹被任命为缅甸政府的新闻局长，次年被任命为缅甸政府新闻部秘书。1953年，吴丹在总理办公室担任负责项目的秘书，1955年任缅甸经济和社会委员会执行秘书，奉命承担更多的职务。

吴丹被任命为联合国代表秘书长时，正担任缅甸大使衔常驻联合国代表(1957-1961)。

在那段时间，他率领缅甸代表团出席联合国大会各届会议，并在1959年担任大会第十四届会议一名副主席。1961年，吴丹任联合国刚果和解委员会主席和联合国资本发展基金委员会主席。

在从事外交工作期间，吴丹曾经几次担任缅甸总理的顾问。

吴丹从1961年11月3日起担任代理秘书长；那一年，联合国大会根据安全理事会的推荐，一致决定任命他填补达格•哈马舍尔德秘书长逝世后未满的任期。后来，大会又在1962年11月30日一致决定任命他为秘书长，任期到1966年11月3日为止。

1966年12月2日，大会根据安全理事会的一致推荐(1966年第229号决议)，任命他连任联合国秘书长，任期到1971年12月31日。

吴丹曾获下列各大学的荣誉(法学博士)学位：加拿大渥太华的卡尔顿大学(1962年5月25日)；马萨诸塞州威廉斯敦的威廉斯学院(1962年6月10日)；新泽西州普林斯顿的普林斯顿大学(1962年6月12日)；马萨诸塞州南哈德利的霍利奥克山学院(1963年6月2日)；马萨诸塞州坎布里奇的哈佛大学(1963年6月13日)；新罕布什尔州汉诺佛的达特默斯学院(1963年6月16日)；加利福尼亚州伯克利的加州大学(1964年4月2日)；科罗拉多州丹佛的丹佛大学(1964年4月3日)；宾夕法尼亚州斯沃思莫尔的斯沃思莫尔学院(1964年6月8日)；纽约市的纽约大学(1964年6月10日)；苏联莫斯科的莫斯科大学(1964年7月30日)；安大略省金斯敦的女王大学(1965年5月22日)；缅因州沃特维尔的科尔比学院(1965年6月6日)；康涅狄格州纽黑文的耶鲁大学(1965年6月14日)；加拿大安大略省温泽的温泽大学(1966年5月28日)；纽约州克林顿的汉密尔顿学院(1966年6月5日)；纽约市布朗克斯区的福德姆大学(1966年6月8日)；纽约市的曼哈顿学院(1966年6月14日)；密歇根州安阿伯的密歇根大学(1967年3月30日)；印度新德里的德里大学(1967年4月13日)；英国利兹大学(1967年5月26日)；比利时布鲁塞尔的卢万大学(1968年4月10日)；加拿大埃德蒙顿的阿尔伯塔大学(1968年5月13日)；马萨诸塞州波士顿的波士顿大学(1968年5月19日)；新泽西州新不伦斯威克的拉特格斯大学(1968年5月29日)；爱尔兰都柏林的都柏林大学圣三学院(1968年7月12日)；加拿大魁北克的拉瓦尔大学(1969年5月31日)；纽约市的哥伦比亚大学(1969年6月3日)；菲律宾大学(1970年4月11日)锡拉丘兹大学(1970年6月6日)。他还获有下列的荣誉学位：第一全球教会神学博士(1970年5月11日)；佛罗里达州迈阿密的佛罗里达国际大学国际法博士(1971年1月25日)；康涅狄格州哈特福德的哈特福德大学法学博士(1971年3月23日)；纽约州汉密尔顿的科尔盖特大学民法博士荣誉学位(1971年5月30日)；北卡罗来纳州达勒姆的杜克大学人文博士(1971年6月7日)。

吴丹于1971年第二个任期届满后退休，晚年久病，终于1974年11月25日逝世，享年65岁。

U Thant , who served as Secretary-General of the United Nations from 1961 to 1971, was chosen to head the world body when Secretary-General Dag Hammarskjold was killed in an air crash in September 1961.

U Thant was born atPantanaw,Burma, on 22 January 1909, and was educated at theNationalHigh Schoolin Pantanaw and atUniversityCollege,Rangoon.

Prior to his diplomatic career, U Thant's experience was in education and information work. He served as Senior Master at theNationalHigh School, which he had attended in Pantanaw, and in 1931, he became Headmaster after winning first place in the Anglo-Vernacular Secondary Teachership Examination.

He was a member ofBurma's Textbook Committee and of the Council of National Education before World War II, and was an Executive Committee member of the Heads of Schools Association. He was also active as a free-lance journalist.

In 1942, U Thant served for a few months as Secretary of Burma's Education Reorganization Committee. In the following year, he returned to theNationalHigh Schoolas Headmaster for another four years.

U Thant was appointed Press Director of the Government of Burma in 1947. In 1948, he became Director of Broadcasting, and in the following year, he was appointed Secretary to the Government of Burma in the Ministry of Information. In 1953, U Thant became Secretary for projects in the Office of the Prime Minister, and in 1955, he was assigned additional duties as Executive Secretary of Burma's Economic and Social Board.

At the time of his appointment as Acting Secretary-General of the United Nations, U Thant had been Permanent Representative ofBurmato the United Nations, with the rank of Ambassador (1957-1961).

During that period, he headed the Burmese delegations to the sessions of the General Assembly, and in 1959, he served as one of the Vice-Presidents of the Assembly's fourteenth session. In 1961, U Thant was Chairman of the United Nations Congo Conciliation Commission and Chairman of the Committee on a United Nations Capital Development Fund.

During his diplomatic career, U Thant served on several occasions as Adviser to Prime Ministers of Burma.

U Thant began serving as Acting Secretary-General since 3 November 1961, when he was unanimously appointed by the General Assembly, on the recommendation of the Security Council, to fill the unexpired term of the late Secretary-General, Dag Hammarskjold. He was then unanimously appointed Secretary-General by the General Assembly on 30 November 1962 for a term of office ending on 3 November 1966.

U Thant was re-appointed for a second term as Secretary-General of the United Nations by the General Assembly on 2 December 1966 on the unanimous recommendation of the Security Council (resolution 229, 1966). His term of office continued until 31 December 1971.

U Thant received honorary degrees (LL.D) from the following universities: Carleton University, Ottawa, Canada (25 May 1962); Williams College, Williamstown, Massachusetts (10 June 1962); Princeton University, Princeton, New Jersey (12 June 1962); Mount Holyoke College, South Hadley, Massachusetts (2 June 1963); Harvard University, Cambridge, Massachusetts (13 June 1963); Dartmouth College, Hanover, New Hampshire (16 June 1963); University of California at Berkeley, California (2 April 1964); University of Denver, Denver, Colorado (3 April 1964); Swarthmore College, Swarthmore, Pennsylvania (8 June 1964); New York University, New York (10 June 1964); Moscow University, Moscow, Soviet Union (30 July 1964); Queen's University, Kingston, Ontario (22 May 1965); Colby College, Waterville, Maine (6 June 1965); Yale University, New Haven, Connecticut (14 June 1965); University of Windsor, Windsor, Ontario, Canada (28 May 1966); Hamilton College, Clinton, New York (5 June 1966); Fordham University, Bronx, New York (8 June 1966); Manhattan College, New York (14 June 1966); University of Michigan, Ann Arbor, Michigan (30 March 1967); Delhi University, New Delhi, India (13 April 1967); University of Leeds, England (26 May 1967); Louvain University, Brussels, Belgium (10 April 1968); University of Alberta, Edmonton, Canada (13 May 1968); Boston Unversity, Boston, Massachusetts (19 May 1968); Rutgers University, New Brunswick, New Jersey (29 May 1968); University of Dublin (Trinity College), Dublin, Ireland (12 July 1968); Laval University, Quebec, Canada (31 May 1969); Columbia University, New York City (3 June 1969); the University of the Philippines (11 April 1970); and Syracuse University (6 June 1970). He also received the following honorary degrees: Doctor of Divinity, The First Universal Church (11 May 1970); Doctor of International Law, Florida International University, Miami, Florida (25 January 1971); Doctor of Laws, University of Hartford, Hartford, Connecticut (23 March 1971); Doctor of Civil Laws degree, honoriscausa, Colgate University, Hamilton, New York, (30 May 1971); Doctor of Humane Letters, Duke University, Durham, North Carolina (7 June 1971).

U Thant retired at the end of his second term in 1971 and he died on 25 November 1974 after a long illness. He was 65 years old.