Born on April 26, 1875, in Whanghai Province, Korea, into a family with ties to a long line of dynastic Korean rulers, Rhee completed a traditional, classical Confucian education before entering an American Methodist mission school. He soon became politically active as a nationalist and member of the Independence Club. He was imprisoned in 1897 for leading demonstrations against the Korean monarchy. At this time, Rhee also became a Christian. Upon his release from prison in 1904, Rhee traveled to the United States, where he obtained, among other degrees, a Ph.D. from Princeton. After six years in the United States, he returned to Korea, now under Japanese rule. His political views and activities soon clashed with the Japanese occupiers, and in 1912 he left again.

In 1919 he was elected president of the Korean Provisional Government in exile, a post he held for 20 years. In 1945 he returned to Korea, now divided into Soviet and U.S. zones of occupation. In 1948, Rhee was elected president of the newly founded South Korean republic. He led a feeble state, beset by economic problems, army mutiny, government infighting and, most of all, a bitter rivalry with North Korea. On June 25, 1950, North Korean troops, aided by the Soviet Union, invaded South Korea. Thanks to the assembly of a U.S.-led U.N. army, Rhee's regime survived. Rhee strongly advocated that the U.N. forces unify his country militarily. However, his allies had more limited goals, causing Rhee to undermine cease-fire talks by unilaterally liberating some 8,000 North Korean prisoners of war in 1953. In spite of Rhee's opposition, a truce went into effect on July 27, 1953.

After the war, Rhee allowed himself to be isolated from events by a small circle of advisers. Because his government was corrupt and intolerant of opponents, particularly from the left, he did not succeed in bringing stability to his country. He was re-elected in 1956 and won another victory in 1960, supposedly with 90 percent of the vote. However, by this time popular resentment of his autocratic regime was giving rise to widespread anti-government demonstrations and civil disorder. In April the unrest culminated in the so-called Student Revolution, which forced his resignation. Rhee went into voluntary exile in Hawaii, where he died in Honolulu on July 19, 1965 at age 90.