Yoon Bo-seon (Hangul/Hanja: 윤보선/尹潽善; Born: August 26th 1897 in Sinhang-ri 143-beonji, Dunpo-myeon, Asan City, Southern Chungcheong Province – Died: July 18th 1990 in AnGuk-dong, Seoul Jongno-gu) was a Korean independence activist and politician, who served as the second President of South Korea from 1960 to 1962 before being replaced by the long-serving Park Chung-hee as a result of the May 16 coup in 1961 which also known as Teachers' Day Coup d'Etat.
Having entered politics after World War II, Yoon served as Secretary to Korea's Chief of Staff in 1947; and was Mayor of Seoul in 1948. He served as Commerce Minister for the newly liberated Korea from 1949–1950. In 1955 Yoon helped establish the South Korean Democratic Party.
Yoon Bo-seon was a son of Yoon Chi-so (윤치소/尹致昭, 1871–1944) and Lady Lee Bum-sook (이범숙/李範淑, 1876–1969). He was a member of Haepyeong Yoon Clan (해평윤씨/海平尹氏), originated from Haepyeong-myeon, Gumi City, Northern Gyeongsang Province - where the Last Empress of Korean Empire, Empress Sunjeonghyo originated from the same clan as President Yoon. Yoon studied in the United Kingdom, graduating with an M.A. from the University of Edinburgh, Scotland in 1930. He returned to Korea in 1932.
Yun entered politics in 1945 following Liberation Day (or Gwangbokjeol). The first Doctor of Philosophy from Princeton University in Korea, as well as first President of South Korea, Dr. Syngman Rhee, was his mentor. By 1947, Yoon was serving as Secretary to the Korean Chief of Staff. In 1948, Rhee appointed Yoon to the position of mayor of Seoul. A year later, he was made Minister of Commerce and Industry. However, Yoon soon began to disagree with Rhee's authoritarian policies.
While serving as president of the Red Cross Society, he was elected to the National Assembly in 1954. A year later, he co-founded the opposition South Korean Democratic Party. In 1959, he became a representative to the Supreme Council of the Democratic Party.
Rhee's government was ousted by a student-led, pro-democracy uprising in 1960; and Yoon was elected president on August 13, and appointed Chang Myon as First Minister. In response to the authoritarian excesses of Rhee's regime, South Korea had switched to a parliamentary system; so in fact Yoon served merely as a figurehead.
Following Park Chung Hee's coup in 1961, Yoon stayed in his post in order to provide some legitimacy to the new regime, but resigned on March 22, 1962. In the following years, Yoon received suspended sentences several times for anti-government activities. He opposed Park's authoritarian rule and ran for president twice, in 1963 and 1967, losing each time. Yoon retired from active politics in 1980 and focused his life on cultural activities until his death on July 18th 1990.