| Ahmad Shah I | Indian king who founded Ahmed… | 1389–1442 |
| Guigo I | Cartusian monk | 1083–1136 |
| Leonidas I | king of Sparta | |
| Louis Philippe I | King of the French | 1773–1850 |
| Mihira Bhoja I | Ruler of the Gurjara Pratihar… | 836–885 |
| Pope Gregory I | Pope from 590 to 604 | 540–604 |
| Pope John Paul I | 263rd Pope of the Catholic Ch… | 1912–1978 |
| Pope Sixtus I | pope | 42 |
| Lee Iacocca | American businessman | 1924–2019 |
| Iamblichus | Syrian philosopher | 240–320 |
| Dolores Ibárruri | Spanish Republican leader of … | 1895–1989 |
| Ibbi-Sin | King of Sumer and Akkad | |
| Eva Ibbotson | British children's writer | 1925–2010 |
| Anwar Ibrahim | Malaysian politician | 1947 |
| Zlatan Ibrahimović | Swedish association football … | 1981 |
| Henrik Ibsen | Norwegian playwright, theatre… | 1828–1906 |
| Masaru Ibuka | Japanese businessman | 1908–1997 |
| Masuji Ibuse | Japanese writer | 1898–1993 |
| David Icke | English writer and public spe… | 1952 |
| Harold L. Ickes | American politician | 1874–1952 |
| Eric Idle | British comedian, actor, sing… | 1943 |
| Frank Iero | American musician | 1981 |
| Gwen Ifill | American journalist, televisi… | 1955–2016 |
| Akira Ifukube | Japanese composer | 1914–2006 |
| Conn Iggulden | British author | 1971 |
| Gabriel Iglesias | American actor | 1976 |
| Julio Iglesias | Spanish recording artist; si… | 1943 |
| Michael Ignatieff | professor at Harvard Kennedy … | 1947 |
| Noel Ignatiev | American historian | 1940–2019 |
| Leo Igwe | Nigerian human rights activist | 1970 |
| Witi Ihimaera | New Zealand writer | 1944 |
| Edward Ihnatowicz | Cybernetic sculptor | 1926–1988 |
| Agis II | King of Sparta | |
| August Heckscher II | American writer | 1913–1997 |
| Constantius II | Roman emperor | 317–361 |
| Henry Ford II | American automotive industry … | 1917–1987 |
| Jerome Foster II | | 2002 |
| John Marshall Harlan II | American judge and Associate … | 1899–1971 |
| Josiah Quincy II | American lawyer | 1744–1775 |
| Mehmed II | Ottoman sultan | 1432–1481 |
| Nakamura Kichiemon II | Japanese kabuki actor (1944-2… | 1944–2021 |
| Oscar Hammerstein II | American librettist, theatric… | 1895–1960 |
| Pope John Paul II | 264th Pope of the Catholic Ch… | 1920–2005 |
| Pope Julius II | pope from 1503 to 1513 | 1443–1513 |
| Pope Pius II | pope | 1405–1464 |
| Pope Urban II | pope | 1035–1099 |
| Robert J. Marks II | American electrical engineeri… | 1950 |
| Shah Alam II | 16th Mughal Emperor | 1728–1806 |
| Umar II | Umayyad caliph | 681–720 |
| William Barber II | civil rights leader from Nort… | 1963 |
| Aga Khan III | 48th Imam of the Nizari Ismai… | 1877–1957 |
| Andre Dubus III | Novelist, short story writer | 1959 |
| Benigno Aquino III | 15th President of the Philipp… | 1960 |
| Ben Witherington III | American religion academic | 1951 |
| Bob Burns III | American film historian and a… | 1935 |
| Carlton Mellick III | American writer | 1977 |
| Edwin Meese III | American presidential advisor | 1931 |
| Ghazi ud-Din Khan Feroze Jung III | Mughal noble | 1736–1800 |
| Henry Lee III | American politician, governor… | 1756–1818 |
| James Morris III | American writer | 1752–1820 |
| Josiah Quincy III | American politician | 1772–1864 |
| Loudon Wainwright III | American singer-songwriter, h… | 1946 |
| Martin Luther King III | Civil right activist | 1957 |
| Mswati III | King of Swaziland | 1968 |
| Napoleon III | French emperor, president, an… | 1808–1873 |
| Pope Eugene III | pope | |
| Thomas Anthony Dooley III | American physician | 1927–1961 |
| William A. Henry III | American critic | 1950–1994 |
| William R. Looney III | 28th Commander, Air Education… | 1949 |
| Sumio Iijima | Japanese nanotechnologist | 1939 |
| Naomi Iizuka | American dramatist | 1965 |
| Chika Ike | Nigerian actress | 1985 |
| Daisaku Ikeda | Japanese writer | 1928 |
| Ikkyu | Japanese Buddhist monk | 1394–1481 |
| Theresa Ikoko | English psychologist, playwri… | |
| Mia Ikumi | Japanese manga artist | 1979 |
| Kancha Ilaiah | Indian scholar, activist and … | 1952 |
| Greg Iles | Novelist | 1960 |
| Immaculée Ilibagiza | Rwandan writer | 1972 |
| Andrey Illarionov | Russian politician | 1961 |
| Ivan Illich | austrian philosopher and theo… | 1926–2002 |
| Josefa Iloilo | President of Fiji | 1920–2011 |
| Kim Il-sung | President of the Democratic P… | 1912–1994 |
| Hugh Iltis | Czech-American botanist and e… | 1925–2016 |
| Iltutmish | Sultan of Mamluk Sultanate | 1210–1236 |
| Masaaki Imai | Japanese business theorist an… | 1930 |
| Neamat Imam | Canadian-Bangladeshi writer | 1971 |
| Blair Imani | American activist | 1993 |
| José Manuel Imbamba | Angolan Roman Catholic archbi… | 1965 |
| Natalie Imbruglia | British-Australian singer and… | 1975 |
| Jörg Immendorff | German artist | 1945–2007 |
| Lex Immers | Dutch footballer | 1986 |
| Chris Impey | astronomer | 1956 |
| Don Imus | Radio personality | 1940–2019 |
| Carrie Ann Inaba | American entertainer | 1968 |
| Keiji Inafune | Japanese video game designer | 1965 |
| Lord Infamous | American rapper | 1975–2013 |
| Leopold Infeld | Polish physicist | 1898–1968 |
| Paul Tan Chee Ing | Malaysian bishop | 1940 |
| John James Ingalls | American politician | 1833–1900 |
