Yen Chia-kan (Chinese: 嚴家淦; pinyin: Yán Jiāgàn; 23 October 1905 – 24 December 1993), also known as C. K. Yen, was a Kuomintang politician. He succeeded Chiang Kai-shek as President of the Republic of China upon Chiang's death on 5 April 1975 and served out the remainder of Chiang's term until 20 May 1978.
He was born in Wu County, Suzhou, Jiangsu province in 1905. He came of a prestigious Suzhou family, the Yan (Yen) Family of Dongshan (東山嚴氏). He graduated from Saint John's University in Shanghai with a degree in chemistry in 1926.
Yen started to work as director of the finance department of Fujian Provincial Government in August 1939. During his term, he initiated a policy of land tax payment for farmers with their agricultural produce. This policy was then adopted nationwide across China and contributed significantly for the nation food supply during World War II.
Yen previously served as Minister of Economic Affairs, minister of finance, and Governor of Taiwan Province. He became premier on 16 December 1963.
In 1966 the National Assembly elected Yen as Vice President and re-elected him in 1972. He became the second President following the death of Chiang Kai-shek and was later succeeded by Chiang's son, Premier Chiang Ching-kuo. After his presidency, Yen served as Chairman of the Council on Chinese Cultural Renaissance and Chairman of Board of the National Palace Museum until 1991.
Yen died in Taipei City at the age of 88. He was buried at the Wuchih Mountain Military Cemetery in New Taipei City.