Authors Born on March 21
- Gary Giddins Jazz Musician, 1948
- Gary Oldman Film Actor, 1958
- George David Birkhoff Mathematician, 1884
- George Edgar Vincent Sociologist, 1864
- H. A. L. Fisher Historian, 1865
- Haddon W. Robinson Professor, 1931
- Halton Arp Astronomer, 1927
- Hans Hofmann Painter, 1880
- Harper Reed Entrepreneur, 1978
- Herbert Albert Laurens Fisher Politician, 1865
- Ian Christe Author, 1970
- Jair Bolsonaro Politician, 1955
- Jaye Davidson Model, 1968
- Jean Paul Writer, 1763
- Jeff Lemire Cartoonist, 1976
- Jim Matheson Politician, 1960
- John Dobbin Painter, 1815
- John Prendergast Human Rights Activist, 1963
- Jonah Goldberg Columnist, 1969
- Joseph Mawle Actor, 1974
- Kaori Ekuni Author, 1964
- Karyn Kusama Film Director, 1968
- Kassie DePaiva Actress, 1961
- Kevin Federline Rapper, 1978
- Lajos Kassak Writer, 1887
- Lauren Kate Author, 1981
- Louise Leakey Paleoanthropologist, 1972
- M. N. Roy Activist, 1887
- Margaret Mahy Author, 1936
- Marit Bjorgen Athlete, 1980
- Mark Waid Writer, 1962
- Mark Williams Snooker Player, 1975
- Matthew Broderick Actor, 1962
- Maxim Musician, 1967
- Michael Foreman Author, 1938
- Mike Jackson Officer, 1944
- Modest Mussorgsky Composer, 1839
- Nick "Peanut" Baines Musician, 1978
- Nirmala Srivastava Guru, 1923
- Nizar Qabbani Diplomat, 1923