List of Famous people born on April 21st

Kang Pan-sŏk was the mother of North Korean leader Kim Il-sung. She came from the village of Chilgol and raised Kim on a small farm in Mangyongdae, both near Pyongyang. She accepted, but rarely participated in her husband's pro-independence activism. After the family fled to Manchuria to avoid arrest, she did not return to Korea. 21 April is a day of memorial for her in North Korea, when a wreath-laying ceremony is held at Chilgol Revolutionary Site.

Halfdan Theodor Mahler was a Danish physician. He served three terms as director-general of the World Health Organization (WHO) from 1973 to 1988, and is widely known for his effort to combat tuberculosis and his role in having shaped the landmark Alma Ata Declaration that defined the Health for All by the Year 2000 strategy.

Sir Walter Robert Buchanan-Riddell, 12th Baronet was a British academic. He was educated at Eton College and Christ Church, Oxford. He was Principal of Hertford College, Oxford between 1922 and 1929.

Michael Hartley Freedman is an American mathematician, at Microsoft Station Q, a research group at the University of California, Santa Barbara. In 1986, he was awarded a Fields Medal for his work on the 4-dimensional generalized Poincaré conjecture. Freedman and Robion Kirby showed that an exotic ℝ⁴ manifold exists.