Syngman Rhee (Korean: 이승만; Hanja: 李承晚; pronounced [iː.sɯŋ.man]; 26 March 1875 – 19 July 1965), also known by his art name Unam (우남; 雩南), was a South Korean politician who served as the first president of South Korea from 1948 to 1960. Rhee was also the first and last president of the Provisional Government of the Republic of Korea from 1919 to his impeachment in 1925 and from 1947 to 1948. As president of South Korea, Rhee's administration was characterised by authoritarianism, limited economic development, and in the late 1950s growing political instability and public opposition to his rule.

Born in Hwanghae Province, Joseon, Rhee attended an American Methodist school, where he converted to Christianity. He became a Korean independence activist and was imprisoned for his activities in 1899. After his release in 1904, he moved to the United States, where he received degrees from American universities and met Presidents Theodore Roosevelt and Woodrow Wilson. After a brief 1910–12 return to Korea, he moved to Hawaii in 1913. In 1919, following the Japanese suppression of the March First Movement, Rhee joined the right-leaning Korean Provisional Government in exile in Shanghai. From 1918 to 1924, he served as the first President of the Korean Provisional Government until 1925. He then returned to the United States, where he advocated and fundraised for Korean independence. In 1939, he moved to Washington, DC. In 1945, he was returned to US-controlled Korea by the US military. On 20 July 1948, he was elected the first president of the Republic of Korea by the National Assembly, ushering in the First Republic of Korea.

As president, Rhee continued his hardline anti-communist and pro-American views that characterized much of his earlier political career. Rhee was president during the outbreak of the Korean War (1950–1953), in which North Korea invaded South Korea. He refused to sign the armistice agreement that ended the war, wishing to have the peninsula reunited by force.

After the fighting ended, South Korea's economy lagged behind North Korea's and was heavily reliant on US aid, despite successful efforts to battle illiteracy. After being re-elected in 1956, he pushed to modify the constitution to remove the two-term limit, despite opposition protests. He was reelected uncontested in March 1960, after his opponent Chough Pyung-ok died from cancer before the election took place. After Rhee's ally Lee Ki-poong won the corresponding vice-presidential election by a wide margin, the opposition rejected the result as rigged, which triggered protests. These escalated into the student-led April Revolution, in which police shot demonstrators in Masan. The resulting scandal caused Rhee to resign on 26 April, ushering in the Second Republic of Korea. Following his resignation, he spent a month at the residence Ihwajang and departed for exile in Hawaii by plane on 29 May. However, according to Rhee, he went to Hawaii for medical treatment. Rhee claimed that he was never in exile – he simply was not able to return to his homeland. He spent the rest of his life in exile in Honolulu, Hawaii, and died of a stroke in 1965.

Syngman Rhee was born on 26 March 1875 in Daegyeong, a village in Pyeongsan County, Hwanghae Province, Joseon. Rhee was the third but only surviving son out of three brothers and two sisters (his two older brothers both died in infancy) in a rural family of modest means. Rhee's family traced its lineage back to King Taejong of Joseon. He was a 16th-generation descendant of Grand Prince Yangnyeong through his second son, Yi Heun who was known as Jangpyeong Dojeong (장평도정; 長平都正). This case makes him a distant relative of the mid-Joseon military officer Yi Sun-sin (not be confused with Admiral Yi Sun-sin). His mother was a member of Gimhae Kim clan.

In 1877, at the age of two, Rhee and his family moved to Seoul, where he had traditional Confucian education in various seodang in Nakdong (낙동; 駱洞) and Dodong (도동; 桃洞). When Rhee was six years old a smallpox infection rendered him virtually blind until he was treated with western medicine, possibly by a Japanese doctor. Rhee was portrayed as a potential candidate for the gwageo, the traditional Korean civil service examination, but in 1894 reforms abolished the gwageo system, and in April he enrolled in the Paechae School [ko], an American Methodist school, where he converted to Christianity. Rhee studied English and sinhakmun (신학문; 新學問; lit. new subjects). Near the end of 1895, he joined a Hyeopseong (Mutual Friendship) Club (협성회; 協成會) created by Philip Jaisohn, who returned from the United States after his exile following the Kapsin Coup. He worked as the head and the main writer of the newspapers Hyŏpsŏnghoe hoebo [ko] and Maeil sinmun [ko], the latter being the first daily newspaper in Korea. During this period, Rhee earned money by teaching the Korean language to Americans. In 1895, Rhee graduated from Pai Chai School.

Rhee became involved in anti-Japanese circles after the end of the First Sino-Japanese War in 1895, which saw Joseon passed from the Chinese sphere of influence to the Japanese. Rhee was implicated in a plot to take revenge for the assassination of Empress Myeongseong, the wife of King Gojong who was assassinated by Japanese agents (known in Korean history as the Chunsaengmun incident [ko]); however, a female American physician Georgiana E. Whiting helped him avoid the charges by disguising him as her patient and go to his sister's house. Rhee acted as one of the forerunners of the Korean independence movement through grassroots organizations such as the Hyeopseong Club and the Independence Club. Rhee organized several protests against corruption and the influences of the Japan and the Russian Empire. As a result, in November 1898, Rhee attained the rank of Uigwan (의관; 議官) in the Imperial Legislature, the Jungchuwon (중추원; 中樞院).

After entering civil service, Rhee was implicated in a plot to remove King Gojong from power through the recruitment of Pak Yŏnghyo. As a result, Rhee was imprisoned in the Gyeongmucheong Prison (경무청; 警務廳) in January 1899. Other sources place the year arrested as 1897 and 1898. Rhee attempted to escape on the 20th day of imprisonment but was caught and was sentenced to life imprisonment through the Pyeongniwon (평리원; 平理院). He was imprisoned in the Hanseong Prison (한성감옥서; 漢城監獄署). In prison, Rhee translated and compiled The Sino–Japanese War Record (청일전기; 淸日戰紀), wrote The Spirit of Independence (독립정신; 獨立精神), compiled the New English–Korean Dictionary (신영한사전; 新英韓辭典) and wrote in the Imperial Newspaper (제국신문; 帝國新聞). He was also tortured. Examples of this included Japanese officers lighting oil paper which were pushed up his fingernails, and then smashing them one-by-one.