Mr. Sithu U Nyun, a national of Myanmar, served as the third Executive Secretary of ECAFE from 1959 to 1973.

U Nyun joined the United Nations in 1951 as Chief of the ECAFE Industry and Trade Division and was appointed Deputy Executive Secretary in 1957. He was appointed Executive Secretary in April 1959. In 1931, he joined the then British colonial civil service in IndialBurma, and had a distinguished career in the administrative service of the Government of Burma before joining the United Nations. Among the various posts he held were those of Under-Secretary and Permanent Secretary in the Ministry of Commerce and Industry. He was leader of Burmese trade missions which concluded trade agreements between Burma and a number of other countries. He also represented Burma at a number of international economic conferences.

He was educated at Rangoon University, Myanmar, the London School of Economics and Political Science and the School of Oriental Studies of London University, the United Kingdom.