On July 20, 1960 (the 27th of the sixth lunar month), Mrs Bandaranaike became Prime Minister of Sri Lanka.

Mrs. Bandaranaike, name Sirimawo-Ratwattai-Diaz. Born on April 17, 1916, Sinhalese, Buddhist. Noble by birth, graduated from St. Bridget's Church Girls' School in Colombo. After marrying Solomon-Bandaranaike, then Minister of Health and Local Administration, in 1940, she began to engage in social welfare work and political activities. She has served as the leader of the Ceylon Rural Women's Association, the All-Ceylon Buddhist Women's Federation, and the Ceylon Cultural Association.

She succeeded as chairman of the Liberal Party after the assassination of her husband, Prime Minister Solomon Bandaranaike in 1959. In the general election of Sri Lanka on July 20, 1960, the Liberal Party defeated the ruling United National Party and Mrs Bandaranaike became Prime Minister. In 1965, he became the leader of the opposition party and formed a cabinet again in May 1970. During his term of office (1960.7-1965.3, 1970.5-1977), he claimed to pursue socialism and advocated neutrality and non-alignment internationally; actively advocated Buddhism and encouraged the development of Sinhala language and culture; attended many heads of state and government meetings of non-aligned countries and visited China several times.