April 21

Pre-1600

 * 753 BC – Romulus founds Rome (traditional date).
 * 43 BC – Battle of Mutina: Mark Antony is again defeated in battle by Aulus Hirtius, who is killed. Antony fails to capture Mutina and Decimus Brutus is murdered shortly after.
 * 900 – The Laguna Copperplate Inscription (the earliest known written document found in what is now the Philippines): the Commander-in-Chief of the Kingdom of Tondo, as represented by the Honourable Jayadewa, Lord Minister of Pailah, pardons from all debt the Honourable Namwaran and his relations.
 * 1092 – The Diocese of Pisa is elevated to the rank of metropolitan archdiocese by Pope Urban II
 * 1506 – The three-day Lisbon Massacre comes to an end with the slaughter of over 1,900 suspected Jews by Portuguese Catholics.
 * 1509 – Henry VIII ascends the throne of England on the death of his father, Henry VII.
 * 1526 – The last ruler of the Lodi dynasty, Ibrahim Lodi is defeated and killed by Babur in the First Battle of Panipat.

1601–1900

 * 1615 – The Wignacourt Aqueduct is inaugurated in Malta.
 * 1782 – The city of Rattanakosin, now known internationally as Bangkok, is founded on the eastern bank of the Chao Phraya River by King Buddha Yodfa Chulaloke.
 * 1789 – John Adams sworn in as first US Vice President (nine days before George Washington).
 * 1789  – George Washington's reception at Trenton is hosted by the Ladies of Trenton as he journeys to New York City for his first inauguration.
 * 1792 – Tiradentes, a revolutionary leading a movement for Brazil's independence, is hanged, drawn and quartered.
 * 1802 – Twelve thousand Wahhabis sack Karbala, killing over three thousand inhabitants.
 * 1806 – Action of 21 April 1806: A French frigate escapes British forces off the coast of South Africa.
 * 1809 – Two Austrian army corps are driven from Landshut by a First French Empire army led by Napoleon as two French corps to the north hold off the main Austrian army on the first day of the Battle of Eckmühl.
 * 1821 – Benderli Ali Pasha arrives in Constantinople as the new Grand Vizier of the Ottoman Empire; he remains in power for only nine days before being sent into exile.
 * 1836 – Texas Revolution: The Battle of San Jacinto: Republic of Texas forces under Sam Houston defeat troops under Mexican General Antonio López de Santa Anna.
 * 1856 – Australian labour movement: Stonemasons and building workers on building sites around Melbourne march from the University of Melbourne to Parliament House to achieve an eight-hour day.
 * 1894 – Norway formally adopts the Krag–Jørgensen bolt-action rifle as the main arm of its armed forces, a weapon that would remain in service for almost 50 years.
 * 1898 – Spanish–American War: The United States Navy begins a blockade of Cuban ports. When the U.S. Congress issued a declaration of war on April 25, it declared that a state of war had existed from this date.

1901–present

 * 1914 – Ypiranga incident: A German arms shipment to Mexico is intercepted by the U.S. Navy near Veracruz.
 * 1918 – World War I: German fighter ace Manfred von Richthofen, better known as "The Red Baron", is shot down and killed over Vaux-sur-Somme in France.
 * 1926 – Al-Baqi cemetery, former site of the mausoleum of four Shi'a Imams, is leveled to the ground by Wahhabis.
 * 1934 – The "Surgeon's Photograph", the most famous photo allegedly showing the Loch Ness Monster, is published in the Daily Mail (in 1994, it is revealed to be a hoax).
 * 1945 – World War II: Soviet forces south of Berlin at Zossen attack the German High Command headquarters.
 * 1946 – The U.S. Weather Bureau publish a paper which stated the width of a tornado which struck the city of Timber Lake, South Dakota was 4 mi, which would make this the widest tornado ever documented in history.
 * 1948 – United Nations Security Council Resolution 47 relating to Kashmir conflict is adopted.
 * 1950 – The Nainital wedding massacre occurs, killing 22 members of the Harijan caste.
 * 1952 – Secretary's Day (now Administrative Professionals' Day) is first celebrated.
 * 1958 – United Air Lines Flight 736 collides with a United States Air Force fighter jet near Arden, Nevada in what is now Enterprise, Nevada.
 * 1960 – Brasília, Brazil's capital, is officially inaugurated. At 09:30, the Three Powers of the Republic are simultaneously transferred from the old capital, Rio de Janeiro.
 * 1962 – The Seattle World's Fair (Century 21 Exposition) opens. It is the first World's Fair in the United States since World War II.
 * 1963 – The first election of the Universal House of Justice is held, marking its establishment as the supreme governing institution of the Baháʼí Faith.
 * 1964 – A Transit-5bn satellite fails to reach orbit after launch; as it re-enters the atmosphere, 2.1 lb of radioactive plutonium in its SNAP RTG power source is widely dispersed.
 * 1965 – The 1964–1965 New York World's Fair opens for its second and final season.
 * 1966 – Rastafari movement: Haile Selassie of Ethiopia visits Jamaica, an event now celebrated as Grounation Day.
 * 1967 – A few days before the general election in Greece, Colonel George Papadopoulos leads a coup d'état, establishing a military regime that lasts for seven years.
 * 1972 – Astronauts John Young and Charles Duke fly Apollo 16's Apollo Lunar Module to the Moon's surface, the fifth NASA Apollo Program crewed lunar landing.
 * 1975 – Vietnam War: President of South Vietnam Nguyễn Văn Thiệu flees Saigon, as Xuân Lộc, the last South Vietnamese outpost blocking a direct North Vietnamese assault on Saigon, falls.
 * 1977 – Annie opens on Broadway.
 * 1982 – Baseball: Rollie Fingers of the Milwaukee Brewers becomes the first pitcher to record 300 saves.
 * 1985 – The compound of the militant group The Covenant, The Sword, and the Arm of the Lord surrenders to federal authorities in Arkansas after a two-day government siege.
 * 1987 – The Tamil Tigers are blamed for a car bomb that detonates in the Sri Lankan capital city of Colombo, killing 106 people.
 * 1989 – Tiananmen Square protests of 1989: In Beijing, around 100,000 students gather in Tiananmen Square to commemorate Chinese reform leader Hu Yaobang.
 * 1993 – The Supreme Court in La Paz, Bolivia, sentences former dictator Luis García Meza to 30 years in jail without parole for murder, theft, fraud and violating the constitution.
 * 2004 – Five suicide car bombers target police stations in and around Basra, killing 74 people and wounding 160.
 * 2010 – The controversial Kharkiv Pact (Russian Ukrainian Naval Base for Gas Treaty) is signed in Kharkiv, Ukraine, by Ukrainian President Viktor Yanukovych and Russian President Dmitry Medvedev; it was unilaterally terminated by Russia on March 31, 2014.
 * 2012 – Two trains are involved in a head-on collision near Sloterdijk, Amsterdam, in the Netherlands, killing one person and injuring 116 others.
 * 2014 – The American city of Flint, Michigan switches its water source to the Flint River, beginning the ongoing Flint water crisis which has caused lead poisoning in up to 12,000 people, and at least 12 deaths from Legionnaires' disease, ultimately leading to criminal indictments against 15 people, five of whom have been charged with involuntary manslaughter.
 * 2019 – Eight bombs explode at churches, hotels, and other locations in Sri Lanka on Easter Sunday, killing at least 269.
 * 2021 – Indonesian Navy submarine KRI Nanggala (402) sinks in the Bali Sea during a military drill, killing all 53 on board.

Pre-1600

 * 1132 – Sancho VI, king of Navarre (d. 1194)
 * 1488 – Ulrich von Hutten, German religious reformer (d. 1523)
 * 1523 – Marco Antonio Bragadin, Venetian lawyer and military officer (d. 1571)
 * 1555 – Ludovico Carracci, Italian painter and etcher (d. 1619)

1601–1900

 * 1619 – Jan van Riebeeck, Dutch founder of Cape Town (d. 1677)
 * 1630 – Pieter Gerritsz van Roestraten, Dutch-English painter (d. 1700)
 * 1631 – Francesco Maidalchini, Catholic cardinal (d. 1700)
 * 1642 – Simon de la Loubère, French mathematician, poet, and diplomat (d. 1729)
 * 1651 – Joseph Vaz, Sri Lankan priest, missionary, and saint (d. 1711)
 * 1652 – Michel Rolle, French mathematician and academic (d. 1719)
 * 1671 – John Law, Scottish economist (d. 1729)
 * 1673 – Wilhelmine Amalia of Brunswick-Lüneburg (d. 1742)
 * 1713 – Louis de Noailles, French general (d. 1793)
 * 1730 – Antonín Kammel, Czech violinist and composer (d. 1788)
 * 1752 – Pierre-Alexandre-Laurent Forfait, French engineer, hydrographer, and politician, French Minister of Marine and the Colonies (d. 1807)
 * 1752  – Humphry Repton, English gardener and author (d. 1818)
 * 1774 – Jean-Baptiste Biot, French physicist, astronomer, and mathematician (d. 1862)
 * 1775 – Alexander Anderson, Scottish-American illustrator and engraver (d. 1870)
 * 1783 – Reginald Heber, English priest (d. 1821)
 * 1790 – Manuel Blanco Encalada, Spanish-Chilean admiral and politician, 1st President of Chile (d. 1876)
 * 1810 – John Putnam Chapin, American politician, 10th Mayor of Chicago (d. 1864)
 * 1811 – Alson Sherman, American merchant and politician, 8th Mayor of Chicago (d. 1903)
 * 1814 – Angela Burdett-Coutts, 1st Baroness Burdett-Coutts, English art collector and philanthropist (d. 1906)
 * 1816 – Charlotte Brontë, English novelist and poet (d. 1855)
 * 1837 – Fredrik Bajer, Danish lieutenant and politician, Nobel Prize laureate (d. 1922)
 * 1838 – John Muir, Scottish-American environmentalist and author (d. 1914)
 * 1854 – William Stang, German-American bishop (d. 1907)
 * 1864 – Max Weber, German economist and sociologist (d. 1920)
 * 1868 – Alfred Henry Maurer, American painter (d. 1932)
 * 1868  – Mary Rogers Miller, American author and educator (d. 1971)
 * 1870 – Edwin Stanton Porter, American director, producer, and screenwriter (d. 1941)
 * 1874 – Vincent Scotto, French composer and actor (d. 1952)
 * 1882 – Percy Williams Bridgman, American physicist and academic, Nobel Prize laureate (d. 1961)
 * 1885 – Tatu Kolehmainen, Finnish runner (d. 1967)
 * 1887 – Joe McCarthy, American baseball manager (d. 1978)
 * 1889 – Marcel Boussac, French businessman (d. 1980)
 * 1889  – Paul Karrer, Russian-Swiss chemist and academic, Nobel Prize laureate (d. 1971)
 * 1889  – Efrem Zimbalist, Sr., Russian-American violinist, composer, and conductor (d. 1985)
 * 1892 – Freddie Dixon, English motorcycle racer and racing driver (d. 1956)
 * 1893 – Romeo Bertini, Italian runner (d. 1973)
 * 1897 – Odd Lindbäck-Larsen, Norwegian Army general and war historian (d. 1975)
 * 1898 – Maurice Wilson, English soldier, pilot, and mountaineer (d. 1934)
 * 1899 – Randall Thompson, American composer and academic (d. 1984)

1901–present

 * 1903 – Luis Saslavsky, Argentinian director, producer, and screenwriter (d. 1995)
 * 1904 – Jean Hélion, French painter (d. 1987)
 * 1904  – Odilo Globocnik, Italian-Austrian SS officer (d. 1945)
 * 1905 – Pat Brown, American lawyer and politician, 32nd Governor of California (d. 1996)
 * 1911 – Ivan Combe, American businessman, developed Clearasil (d. 2000)
 * 1911  – Kemal Satır, Turkish physician and politician  (d. 1991)
 * 1912 – Eve Arnold, Russian-American photojournalist (d. 2012)
 * 1912  – Marcel Camus, French director and screenwriter (d. 1982)
 * 1913 – Norman Parkinson, English photographer (d. 1990)
 * 1914 – Angelo Savoldi, Italian-American wrestler and promoter, co-founded International World Class Championship Wrestling (d. 2013)
 * 1915 – Garrett Hardin, American ecologist, author, and academic (d. 2003)
 * 1915  – Anthony Quinn, Mexican-American actor (d. 2001)
 * 1916 – Estella B. Diggs, American businesswoman and politician (d. 2013)
 * 1918 – Eddy Christiani, Dutch singer-songwriter and guitarist (d. 2016)
 * 1919 – Don Cornell, American singer (d. 2004)
 * 1919  – Roger Doucet, Canadian tenor (d. 1981)
 * 1919  – Licio Gelli, Italian financer (d. 2015)
 * 1922 – Alistair MacLean, Scottish novelist and screenwriter (d. 1987)
 * 1922  – Allan Watkins, Welsh-English cricketer (d. 2011)
 * 1923 – John Mortimer, English lawyer and author (d. 2009)
 * 1924 – Ira Louvin, American singer-songwriter and mandolin player (d. 1965)
 * 1925 – Anthony Mason, Australian soldier and judge, 9th Chief Justice of Australia
 * 1925  – John Swinton of Kimmerghame, English general and politician, Lord Lieutenant of Berwickshire (d. 2018)
 * 1926 – Elizabeth II, Queen of the United Kingdom and her other realms (d. 2022)
 * 1926  – Arthur Rowley, English footballer, manager, and cricketer (d. 2002)
 * 1927 – Ahmed Arif, Turkish poet and author (d. 1991)
 * 1928 – Jack Evans, Welsh-Canadian ice hockey player and coach (d. 1996)
 * 1930 – Hilda Hilst, Brazilian author, poet, and playwright (d. 2004)
 * 1930  – Silvana Mangano, Italian actress (d. 1989)
 * 1930  – Dieter Roth, German-Swiss illustrator and sculptor (d. 1998)
 * 1930  – Jack Taylor, English footballer and referee (d. 2012)
 * 1931 – Morgan Wootten, American high school basketball coach (d. 2020)
 * 1932 – Slide Hampton, African-American trombonist and composer (d. 2021)
 * 1932  – Elaine May, American actress, comedian, director, and screenwriter
 * 1932  – Angela Mortimer, English tennis player
 * 1933 – Edelmiro Amante, Filipino lawyer and politician (d. 2013)
 * 1933  – Easley Blackwood, Jr., American pianist, composer, and educator (d. 2023)
 * 1933  – Ignatius Zakka I Iwas, Iraqi patriarch (d. 2014)
 * 1935 – Charles Grodin, American actor and talk show host (d. 2021)
 * 1935  – Thomas Kean, American academic and politician, 48th Governor of New Jersey
 * 1936 – James Dobson, American evangelist, psychologist, and author, founded Focus on the Family
 * 1936  – Reg Fleming, Canadian-American ice hockey player (d. 2009)
 * 1937 – Gary Peters, American baseball player (d. 2023)
 * 1937  – Ben Zinn, Israeli-born American academic and former international soccer player
 * 1939 – John McCabe, English pianist and composer (d. 2015)
 * 1939  – Sister Helen Prejean, American nun, activist, and author
 * 1939  – Reni Santoni, American actor (d. 2020)
 * 1940 – Jacques Caron, Canadian ice hockey player and coach
 * 1940  – Souleymane Cissé, Malian director, producer, and screenwriter
 * 1941 – David L. Boren, American lawyer and politician, 21st Governor of Oklahoma
 * 1942 – Geoffrey Palmer, New Zealand politician, 33rd Prime Minister of New Zealand
 * 1945 – Srinivasaraghavan Venkataraghavan, Indian cricketer and umpire
 * 1945  – Mark Wainberg, Canadian researcher and HIV/AIDS activist (d. 2017)
 * 1945  – Diana Darvey, English actress, singer and dancer (d. 2000)
 * 1947 – Al Bumbry, American baseball player
 * 1947  – Iggy Pop, American singer-songwriter, producer, and actor
 * 1947  – John Weider, English bass player
 * 1948 – Gary Condit, American businessman and politician
 * 1948  – Paul Davis, American singer-songwriter and musician (d. 2008)
 * 1948  – Josef Flammer, Swiss ophthalmologist
 * 1948  – Dieter Fromm, German runner
 * 1949 – Patti LuPone, American actress and singer
 * 1950 – Shivaji Satam, Indian actor
 * 1951 – Tony Danza, American actor and producer
 * 1951  – Michael Freedman, American mathematician and academic
 * 1951  – Bob Varsha, American sportscaster
 * 1951  – Steve Vickers, Canadian ice hockey player
 * 1952 – Gerald Early, American author and academic
 * 1952  – Cheryl Gillan, British businesswoman and politician, Secretary of State for Wales (d. 2021)
 * 1953 – John Brumby, Australian politician, 45th Premier of Victoria
 * 1954 – Ebiet G. Ade, Indonesian singer-songwriter and guitarist
 * 1954  – James Morrison, American actor, director, producer, and screenwriter
 * 1954  – Mike Wingfield, South African academic and scientist
 * 1955 – Murathan Mungan, Turkish author, poet, and playwright
 * 1956 – Peter Kosminsky, English director, producer, and screenwriter
 * 1956  – Phillip Longman, German-American demographer and journalist
 * 1957 – Hervé Le Tellier, French linguist and author
 * 1957  – Herbert Wetterauer, German painter, sculptor, and author
 * 1958 – Andie MacDowell, American model, actress, and producer
 * 1958  – Yoshito Usui, Japanese illustrator (d. 2009)
 * 1958  – Michael Zarnock, American author
 * 1959 – Tim Jacobus, American illustrator and painter
 * 1959  – Robert Smith, English singer-songwriter and guitarist
 * 1961 – David Servan-Schreiber, French physician, neuroscientist, and author (d. 2011)
 * 1963 – Ken Caminiti, American baseball player (d. 2004)
 * 1965 – Fiona Kelleghan, American academic, critic and librarian
 * 1969 – Toby Stephens, English actor
 * 1970 – Rob Riggle, American actor and comedian
 * 1971 – Michael Turner, American author and illustrator (d. 2008)
 * 1973 – Steve Backshall, English naturalist, writer, and television presenter
 * 1977 – Gyula Koi, Hungarian scholar and educator
 * 1979 – Virginie Basselot, French chef
 * 1979  – James McAvoy, Scottish actor
 * 1980 – Tony Romo, American football player and announcer
 * 1983 – Tarvaris Jackson, American football player (d. 2020)
 * 1988 – Ricky Berens, American swimmer
 * 1988  – Jencarlos Canela, American singer-songwriter and actor
 * 1989 – Nikki Cross, Scottish wrestler
 * 1992 – Isco, Spanish footballer
 * 1992  – Joc Pederson, American baseball player
 * 1994 – Ludwig Augustinsson, Swedish footballer
 * 1996 – Arianne Hartono, Dutch tennis player
 * 1997 – Mikel Oyarzabal, Spanish footballer
 * 1998 – Jarrett Allen, American basketball player
 * 2003 – Xavi Simons, Dutch footballer
 * 2007 – Princess Isabella of Denmark, daughter of King Frederik X and Queen Mary of Denmark

Pre-1600

 * 234 – Emperor Xian of Han, Chinese emperor (b. 181)
 * 586 – Liuvigild, king of the Visigoths
 * 847 – Odgar, Frankish archbishop of Mainz
 * 866 – Bardas, de facto regent of the Byzantine Empire
 * 941 – Bajkam, de facto regent of the Abbasid Caliphate
 * 1073 – Pope Alexander II
 * 1109 – Anselm of Canterbury, Italian-English archbishop and saint (b. 1033)
 * 1136 – Stephen, Count of Tréguier Breton noblemen (b. c. 1058/62)
 * 1142 – Peter Abelard, French philosopher and theologian (b. 1079)
 * 1213 – Maria of Montpellier, Lady of Montpellier, Queen of Aragon (b. 1182)
 * 1329 – Frederick IV, Duke of Lorraine (b. 1282)
 * 1400 – John Wittlebury, English politician (b. 1333)
 * 1509 – Henry VII of England (b. 1457)
 * 1557 – Petrus Apianus, German mathematician and astronomer (b. 1495)
 * 1574 – Cosimo I de' Medici, Grand Duke of Tuscany (b. 1519)
 * 1591 – Sen no Rikyū, Japanese exponent of the tea ceremony (b. 1522)

1601–1900

 * 1650 – Yagyū Jūbei Mitsuyoshi, Japanese samurai (b. 1607)
 * 1668 – Jan Boeckhorst, Flemish painter (b. c. 1604)
 * 1699 – Jean Racine, French playwright and poet (b. 1639)
 * 1719 – Philippe de La Hire, French mathematician and astronomer (b. 1640)
 * 1720 – Antoine Hamilton, Irish-French soldier and author (b. 1646)
 * 1722 – Robert Beverley, Jr., English historian and author (b. 1673)
 * 1736 – Prince Eugene of Savoy (b. 1663)
 * 1740 – Thomas Tickell, English poet and author (b. 1685)
 * 1758 – Francesco Zerafa, Maltese architect (b. 1679)
 * 1815 – Joseph Winston, American soldier and politician (b. 1746)
 * 1825 – Johann Friedrich Pfaff, German mathematician and academic (b. 1765)
 * 1852 – Ivan Nabokov, Russian general (b. 1787)
 * 1863 – Sir Robert Bateson, 1st Baronet, Irish politician (b. 1782)
 * 1900 – Vikramatji Khimojiraj, Indian ruler (b. 1819)

1901–present

 * 1910 – Mark Twain, American novelist, humorist, and critic (b. 1835)
 * 1918 – Manfred von Richthofen, German captain and pilot (b. 1892)
 * 1924 – Eleonora Duse, Italian actress (b. 1858)
 * 1930 – Robert Bridges, English poet and author (b. 1844)
 * 1932 – Friedrich Gustav Piffl, Bohemian cardinal (b. 1864)
 * 1938 – Allama Muhammad Iqbal, Pakistani National philosopher and poet (b. 1877)
 * 1941 – Fritz Manteuffel, German gymnast (b. 1875)
 * 1945 – Walter Model, German field marshal (b. 1891)
 * 1946 – John Maynard Keynes, English economist and philosopher (b. 1883)
 * 1948 – Aldo Leopold, American ecologist and author (b. 1887)
 * 1952 – Leslie Banks, American actor, director and producer (b. 1890)
 * 1954 – Emil Leon Post, Polish-American mathematician and logician (b. 1897)
 * 1956 – Charles MacArthur, American playwright and screenwriter (b. 1895)
 * 1965 – Edward Victor Appleton, English-Scottish physicist and academic, Nobel Prize laureate (b. 1892)
 * 1971 – François Duvalier, Haitian physician and politician, 40th President of Haiti (b. 1907)
 * 1973 – Arthur Fadden, Australian accountant and politician, 13th Prime Minister of Australia (b. 1894)
 * 1973  – Kemal Tahir, Turkish journalist and author (b. 1910)
 * 1977 – Gummo Marx, American vaudevillian and talent agent (b. 1892)
 * 1978 – Sandy Denny, English singer-songwriter (b. 1947)
 * 1978  – Thomas Wyatt Turner, American biologist and academic (b. 1877)
 * 1980 – Alexander Oparin, Russian biochemist and academic (b. 1894)
 * 1980  – Sohrab Sepehri, Iranian poet and painter (b. 1928)
 * 1983 – Walter Slezak, Austrian-American actor and singer (b. 1902)
 * 1984 – Marcel Janco, Romanian-Israeli artist (b. 1895)
 * 1984  – Hristo Prodanov, Bulgarian engineer and mountaineer (b. 1943)
 * 1985 – Rudi Gernreich, Austrian-American fashion designer, created the monokini (b. 1922)
 * 1985  – Tancredo Neves, Brazilian banker and politician, Prime Minister of Brazil (b. 1910)
 * 1986 – Marjorie Eaton, American painter and actress (b. 1901)
 * 1986  – Salah Jahin, Egyptian poet, playwright, and composer (b. 1930)
 * 1987 – Gustav Bergmann, Austrian-American philosopher from the Vienna Circle (b. 1906)
 * 1990 – Erté, Russian-French illustrator (b. 1892)
 * 1991 – Willi Boskovsky, Austrian violinist and conductor (b. 1909)
 * 1992 – Väinö Linna, Finnish author (b. 1920)
 * 1996 – Abdul Hafeez Kardar, Pakistani cricketer (b. 1925)
 * 1996  – Jimmy Snyder, American sportscaster (b. 1919)
 * 1998 – Jean-François Lyotard, French sociologist and philosopher (b. 1924)
 * 1999 – Buddy Rogers, American actor (b. 1904)
 * 2003 – Nina Simone, American singer-songwriter, pianist, and activist (b. 1933)
 * 2005 – Zhang Chunqiao, Chinese writer and politician, member of the Gang of Four (b. 1917)
 * 2010 – Gustav Lorentzen, Norwegian singer-songwriter and guitarist (b. 1947)
 * 2010  – Juan Antonio Samaranch, Spanish businessman, seventh President of the International Olympic Committee (b. 1920)
 * 2010  – Kanagaratnam Sriskandan, Sri Lankan-English engineer and civil servant (b. 1930)
 * 2011 – Catharina Halkes, Dutch theologian and academic (b. 1920)
 * 2012 – Doris Betts, American author and academic (b. 1932)
 * 2013 – Shakuntala Devi, Indian mathematician and astrologer (b. 1929)
 * 2013  – Leopold Engleitner, Austrian Holocaust survivor, author, and educator (b. 1905)
 * 2014 – George H. Heilmeier, American engineer (b. 1936)
 * 2014  – Win Tin, Burmese journalist and politician, co-founded the National League for Democracy (b. 1930)
 * 2016 – Prince, American singer-songwriter, guitarist, producer, and actor (b. 1958)
 * 2017 – Ugo Ehiogu, English footballer (b. 1972)
 * 2018 – Nabi Tajima, Japanese supercentenarian (b. 1900)
 * 2019 – Polly Higgins, Scottish barrister, author and environmental lobbyist (b. 1968)
 * 2024 – Terry A. Anderson, American journalist (b. 1947)

Holidays and observances

 * Christian feast day:
 * Abdecalas
 * Anastasius Sinaita
 * Anselm of Canterbury
 * Beuno
 * Conrad of Parzham
 * Holy Infant of Good Health
 * Shemon Bar Sabbae
 * Wolbodo
 * April 21 (Eastern Orthodox liturgics)
 * Parilia (ancient Rome)
 * Civil Service Day (India)
 * Grounation Day (Rastafari)
 * Heroic Defense of Veracruz (Mexico)
 * Kang Pan-sok's Birthday (North Korea)
 * Kartini Day (Indonesia)
 * Local Self Government Day (Russia)
 * National Tea Day (United Kingdom)
 * National Tree Planting Day (Kenya)
 * San Jacinto Day (Texas)
 * Queen or King's Official Birthday (Falkland Islands)
 * Tiradentes' Day (Brazil)
 * Vietnam Book Day (Vietnam)