April 20 is the 110th day of the year (111th in leap years) in the Gregorian calendar. There are 255 days remaining until the end of the year.
- 1303 - University of Rome La Sapienza is founded by Pope Boniface VIII.
- 1453 – Last naval battle in Byzantine history, as three Genoese galleys escorting a Byzantine transport fight their way through the huge Ottoman blockade fleet into the Golden Horn.
- 1534 – Jacques Cartier sets sail from France on an expedition that will take him to present-day Canada, including Labrador.
- 1653 – Oliver Cromwell dissolves the Rump parliament.
- 1657 – Freedom of religion is granted to Jews in New Amsterdam, present-day New York City.
- 1689 - James II of England/James VII of Scotland lays siege to Derry in present-day Northern Ireland.
- 1770 - Irekle II, King of Georgia, abandoned by his Russian ally Count Totleben, wins against Ottoman Empire forces at Aspindza.
- 1775 – American Revolutionary War: The Siege of Boston begins.
- 1792 – France declares war on Francis II, Holy Roman Emperor.
- 1810 – The Governor of Caracas (Venezuela), declares independence from Spain.
- 1828 – René Caillié becomes the first non-Muslim to enter Timbuktu.
- 1836 - United States Congress passes the act creating the Wisconsin territory.
- 1862 – Louis Pasteur and Claude Bernard complete the first pasteurization process.
- 1876 - The April Uprising begins in Bulgaria.
- 1887 – The first car race is held in France, on a course running from Paris to Versailles.
- 1889 – Nazi leader Adolf Hitler is born in Braunau am Inn, Austria.
- 1902 – Marie Curie and Pierre Curie refine Radium.
- 1912 – Baseball: The Tiger Stadium (Detroit) and Fenway Park (Boston) open.
- 1914 - 19 people die in the Ludlow massacre in Colorado during a coal miners strike.
- 1916 - In baseball, the Chicago Cubs play their first game at Weeghman Park, now called Wrigley Field, defeating the Cincinnati Reds 7-6.
- 1920 – The 1920 Summer Olympics in Antwerp begin.
- 1922 - The Soviet government creates the South Ossetian Autonomous Oblast within the Georgian Soviet Socialist Republic.
- 1939 - Billie Holiday records the first civil rights song Strange Fruit.
- 1944 - Dutch freighter Voorbode explodes in the harbor of Bergen, Norway, killing 150 people.
- 1945 – World War II: US troops capture Leipzig, which is later handed to Soviet forces.
- 1945 – World War II: At the Führerbunker, Adolf Hitler makes his last outside appearance, handing Iron Cross medals to members of the Hitler Youth on his 56th birthday.
- 1946 - The League of Nations officially dissolves, giving most of its powers to the United Nations.
- 1947 – King Christian X of Denmark dies. King Frederick IX of Denmark succeeds him.
- 1951 - Dan Gavriliu performs the first surgical replacement of a human organ.
- 1964 – The British TV Channel BBC Two begins transmission, but a power cut occurs, due to a fire at Battersea Power Station in London.
- 1967 - A Globe Air plane crashes against a mountain near Nicosia, Cyprus, killing 126 people.
- 1968 - A South African Airways plane crashes shortly after take-off from Windhoek, Namibia, killing 129 people.
- 1968 - Pierre Trudeau becomes Prime Minister of Canada.
- 1968 – British politician Enoch Powell makes his controversial "Rivers of Blood" speech, in which he calls for tighter immigration controls.
- 1972 – Apollo 16 lands on the Moon.
- 1978 – Korean Air Flight 902 is shot down by the Soviets.
- 1986 – Vladimir Horowitz performs in Russia for the first time in 61 years.
- 1986 - Chicago Bulls basketball star Michael Jordan scores a playoff record 63 points in a single game, against the Boston Celtics.
- 1989 – Scientists announce that an Asteroid has narrowly missed hitting the Earth.
- 1992 - Surviving members of the band Queen hold a tribute concert to Freddie Mercury at Wembley Stadium.
- 1998 – The Red Army Faction announces an end to its operations.
- 1999 – Eric Harris and Dylan Klebold, two teenagers, go on a shooting spree at Columbine High School, near Littleton, Colorado.
- 2005 – In Ecuador, President Lucio Gutiérrez is removed by Parliament and replaced by Alfredo Palacio.
- 2007 - Johnson Space Center shooting: A man with a handgun barricades himself in the Johnson Space Center in Houston, Texas, and kills a male hostage before killing himself.
- 2008 – Danica Patrick wins the Indy Japan 300, becoming the first woman to win an Indy car race.
- 2010 – Deepwater Horizon oil spill: An explosion occurs on the Deepwater Horizon Oil rig, near Louisiana in the Gulf of Mexico, killing 11 people, and causing the worst Oil spill in US history.
- 2011 – Photojournalist Tim Hetherington and journalist Chris Hondros are killed in Libya during the 2011 Libyan civil war.
- 2012 - A Bhoja Air plane crashes near Islamabad, Pakistan, killing 127 people.
- 2013 - At least 160 people are killed after an earthquake of over magnitude 6 strikes Sichuan province in China.
- 2013 - Giorgio Napolitano is elected to a second term as President of Italy. It is the first time that an Italian President has been elected to a second term in office.
- 2017 - In Paris, shooting toward police officers killed one officer and the attacker.
- 570 – Muhammad the Prophet, founder of Islam (d. 632)
- 1492 - Pietro Aretino, Italian writer and poet (d. 1556)
- 1494 – Johannes Agricola, German religious reformer (d. 1566)
- 1586 – Saint Rose of Lima, Peruvian saint (d. 1617)
- 1633 – Emperor Go-Komyo, Emperor of Japan (d. 1654)
- 1723 - Cornelius Harnett, American merchant, farmer and statesman (d. 1781)
- 1745 - Philippe Pinel, French physician (d. 1826)
- 1748 – Georg Michael Telemann, German composer (d. 1839)
- 1808 – Emperor Napoleon III of France (d. 1873)
- 1809 - James David Forbes, Scottish physicist and glaciologist (d. 1868)
- 1818 - Albrecht von Stosch, German general and admiral (d. 1896)
- 1839 – King Carol I of Romania (d. 1914)
- 1842 - John Murphy Farley, Irish-American cardinal (d. 1918)
- 1850 - Daniel Chester French, American sculptor (d. 1931)
- 1851 – Torakusu Yamaha, Japanese entrepreneur (d. 1916)
- 1851 – Young Tom Morris, Scottish golfer (d. 1875)
- 1851 - Eduardo Acevedo Díaz, Uruguayan writer and politician (d. 1921)
- 1852 - John Murphy Farley, Archbishop of New York and cardinal (d. 1918)
- 1855 – Inukai Tsuyoshi, Prime Minister of Japan (d. 1932)
- 1859 - Vincenzo Cerulli, Italian astronomer (d. 1927)
- 1860 - Pieter Jelles Troelstra, Dutch-Frisian poet and politician (d. 1930)
- 1871 - Sydney Chapman, British economist (d. 1951)
- 1871 - Slavoljub Eduard Penkala, Croatian engineer and inventor (d. 1972)
- 1875 - Vladimir Vidric, Croatian poet (d. 1989)
- 1879 - Paul Poiret, French fashion designer (d. 1944)
- 1884 – Daniel Varujan, Armenian poet (d. 1915)
- 1884 – Princess Beatrice of Edinburgh and Saxe-Coburg and Gotha (d. 1966)
- 1889 – Adolf Hitler, Nazi leader (d. 1945)
- 1890 – Adolf Schaerf, President of Austria (d. 1965)
- 1890 – Maurice Duplessis, Premier of Quebec (d. 1959)
- 1893 – Joan Miró, Spanish painter (d. 1983)
- 1893 – Edna Parker, American supercentenarian, oldest person in the world at the time of her death (d. 2008)
- 1893 – Harold Lloyd, American actor (d. 1971)
- 1895 - Emile Christian, American jazz musician (d. 1973)
- 1896 - Wop May, Canadian pilot and captain (d. 1952)
- 1904 – Bruce Cabot, American actor (d. 1972)
- 1904 - George Stibitz, American scientist (d. 1995)
- 1908 - Lionel Hampton, American jazz musician, bandleader and actor (d. 2002)
- 1910 – Robert F. Wagner, Jr., Mayor of New York City (d. 1991)
- 1911 – Kukrit Pramoj, Prime Minister of Thailand (d. 1995)
- 1913 - Roger Rochard, French long-distance runner (d. 1993)
- 1914 - Betty Lou Gerson, American actress (d. 1999)
- 1918 – Kai Siegbahn, Swedish physicist (d. 2007)
- 1920 – John Paul Stevens, American jurist (d. 2019)
- 1923 - Mother Angelica, American nun and broadcaster (d. 2016)
- 1923 - Tito Puente, American jazz musician and producer (d. 2000)
- 1923 - Jorge Romo, Mexican footballer (d. 2014)
- 1924 – Leslie Phillips, British actor
- 1924 - Nina Foch, Dutch-American actress (d. 2008)
- 1925 - Elena Verdugo, American actress (d. 2017)
- 1927 – Karl Alexander Müller, Swiss physicist
- 1927 – Phil Hill, American racing driver (d. 2008)
- 1928 - Robert Byrne, American chess player (d. 2013)
- 1928 - Arvo Kruusement, Estonian movie director
- 1930 - Dwight Gustafson, American composer and conductor (d. 2014)
- 1935 - Mario Camus, Spanish screenwriter and movie director
- 1936 – Pat Roberts, United States Senator
- 1936 - Pauli Ellefsen, 6th Prime Minister of the Faroe Islands (d. 2012)
- 1937 – Jiri Dienstbier, Czech politician and journalist (d. 2011)
- 1937 – George Takei, American actor
- 1938 - Betty Cuthbert, Australian athlete (d. 2017)
- 1938 - Igor Sergeyev, Marshal of the Russian Federation (d. 2006)
- 1938 – Peter Snow, British broadcaster
- 1939 - Peter S. Beagle, American writer
- 1939 – Gro Harlem Brundtland, former Prime Minister of Norway
- 1939 - Wayson Choy, Canadian writer (d. 2019)
- 1940 - James Gammon, American actor (d. 2010)
- 1941 - Ryan O'Neal, American actor
- 1942 – Arto Paasilinna, Finnish writer (d. 2018)
- 1943 – Alan Beith, British politician, former MP for Berwick-upon-Tweed
- 1943 - John Eliot Gardiner, British conductor
- 1943 – Edie Sedgwick, American actress (d. 1971)
- 1945 - Michael Brandon, American actor
- 1945 - Gregory Olsen, American entrepreneur
- 1945 - Gerry Steinberg, English politician (d. 2015)
- 1945 - Thein Sein, President of Burma
- 1946 – Sabine Bergmann-Pohl, German politician
- 1947 - David Leland, British director, actor and screenwriter
- 1947 - Björn Skifs, Swedish singer-songwriter, actor and screenwriter
- 1949 – Massimo D'Alema, former Prime Minister of Italy
- 1949 – Aleksandr Maltsev, Russian ice hockey player
- 1949 – Jessica Lange, American actress
- 1949 – Toller Cranston, Canadian figure skater (d. 2015)
- 1949 - Paul Heiney, English journalist
- 1950 - N. Chandrababu Naidu, Indian politician, 13th Chief Minister of Andhra Pradesh
- 1950 – Alexander Lebed, Russian general and politician (d. 2002)
- 1950 - Ibrahim Yusri, Egyptian actor (d. 2015)
- 1951 – Luther Vandross, American singer (d. 2005)
- 1952 - Eric Pickles, British politician
- 1953 – Sebastian Faulks, British writer
- 1956 – Kevin Judge, American Internet Security Expert
- 1958 - Viacheslav Fetisov, Russian ice hockey player
- 1959 – Clint Howard, American actor
- 1960 - Miguel Diaz-Canel, President of Cuba
- 1961 – Nicholas Lyndhurst, British actor
- 1961 - Paul Usher, British actor
- 1962 - Sigurdur Ingi Johannsson, former Prime Minister of Iceland
- 1963 - Rachel Whiteread, British artist and sculptor
- 1964 – Andy Serkis, British actor
- 1964 - Crispin Glover, American actor
- 1964 - Rosalynn Summers, American figure skater
- 1965 - Susan Cookson, British actress
- 1965 - April March, American singer-songwriter
- 1965 - Bernardo Fernando da Silva, Brazilian footballer
- 1966 – David Chalmers, Australian philosopher
- 1966 - David Filo, American businessman and co-founder of Google
- 1967 - Mike Portnoy, American musician
- 1967 – Raymond van Barneveld, Dutch darts player
- 1968 - Julia Morris, Australian actress and television presenter
- 1969 - Felix Baumgartner, Austrian skydiver
- 1970 - Shemar Moore, American actor
- 1972 – Carmen Electra, American actress, singer and model
- 1972 – Marko Kon, Serbian composer, singer and actor
- 1972 - Stephen Marley, Jamaican musician
- 1976 – Aldo Bobadilla, Paraguayan footballer
- 1976 – Shay Given, Irish footballer
- 1976 - Joey Lawrence, American actor
- 1976 - Chris Mason, Canadian ice hockey player
- 1979 - Gregor Tait, Scottish swimmer
- 1979 – Ludovic Magnin, Swiss footballer
- 1980 - Vibeke Skofterud, Norwegian cross-country skier (d. 2018)
- 1980 – Jasmin Wagner, German singer
- 1980 – Lee Wilkie, Scottish footballer
- 1981 - Mike Blair, Scottish rugby union player and coach
- 1983 – Miranda Kerr, Australian supermodel
- 1983 - Danny Granger, American actor, producer and musician
- 1984 - Nelson Evora, Portuguese athlete
- 1984 - Edixon Perea, Colombian footballer
- 1985 – Brent Seabrook, Canadian ice hockey player
- 1985 - Curt Hawkins, American professional wrestler
- 1987 - John Patrick Amedori, American actor
- 1987 - Anna Rossinelli, Swiss singer
- 1991 - Thomas Curtis, American actor
- 1991 - Ondrej Krajak, Czech footballer
- 1992 - Ashton Moio, American actor, stuntman and martial artist
- 1997 - Alexander Zverev, German tennis player
- 1999 - Carly Rose Sonenclar, American actress
- 2000 – Funny Cide, American racehorse
- 689 - Caedwalla, King of Wessex
- 1176 - Richard de Clare, 2nd Earl of Pembroke, English military leader (b. 1130)
- 1314 – Pope Clement V (b. 1264)
- 1517 - Bogdan III the One-Eyed, Romanian son of Stephen of Moldavia (b. 1470)
- 1521 – Zhengde Emperor of China (b. 1491)
- 1526 – Ibrahim Lodi, Sultan of Delhi
- 1534 - Elizabeth Barton, English nun and saint (b. 1506)
- 1558 - Johannes Bugenhagen, German priest and theologian (b. 1485)
- 1769 – Pontiac, Chief of the Ottawa (b. 1720)
- 1786 – John Goodricke, English astronomer (b. 1746)
- 1812 – George Clinton, US Vice President and Governor of New York (b. 1739)
- 1831 - John Abernethy, English surgeon (b. 1864)
- 1869 - Carl Loewe, German composer (b. 1796)
- 1873 - William Tite, English architect (b. 1798)
- 1874 - Alexander H. Bailey, American politician (b. 1817)
- 1887 – Muhammad Sharif Pasha, Egyptian statesman (b. 1826)
- 1899 – Joseph Wolf, German artist (b. 1820)
- 1902 - Joaquim de Sousa Andrade, Brazilian poet (b. 1833)
- 1912 – Bram Stoker, Irish writer (b. 1847)
- 1912 - Pedro Lira, Chilean painter (b. 1845)
- 1914 - Ivar Wickman, Swedish physician (b. 1872)
- 1918 – Karl Ferdinand Braun, German physicist (b. 1850)
- 1927 - Enrique Simonet, Spanish painter (b. 1866)
- 1929 - Prince Albert Wilhelm Heinrich of Prussia (b. 1862)
- 1932 - Giuseppe Peano, Italian mathematician (b. 1858)
- 1935 - John Cameron, Scottish footballer (b. 1872)
- 1937 - James Gillett, 22nd Governor of California (b. 1860)
- 1947 – King Christian X of Denmark (b. 1870)
- 1951 – Ivanoe Bonomi, Prime Minister of Italy (b. 1873)
- 1967 - Leo-Paul Desrosiers, French-Canadian journalist and novelist (b. 1896)
- 1982 - Archibald MacLeish, American poet and writer (b. 1892)
- 1990 - Horst Sindermann, German politician (b. 1915)
- 1991 – Don Siegel, American movie director (b. 1912)
- 1992 - Benny Hill, British comedian and actor (b. 1924)
- 1993 - Cantinflas, Mexican comedian and actor (b. 1911)
- 1994 - Jean Carmet, French actor (b. 1920)
- 1996 - Tran Van Tra, Vietnamese general and politician (b. 1918)
- 1996 – Christopher Robin Milne, son of the writer A. A. Milne (b. 1920)
- 1999 - Deaths in the Columbine High School massacre:
- Cassie Bernall, victim of the Columbine High School massacre (b. 1981)
- Rachel Joy Scott, victim of the Columbine High School massacre (b. 1981)
- Eric Harris, perpetrator of the Columbine High School massacre (b. 1981)
- Dylan Klebold, perpetrator of the Columbine High School massacre (b. 1981)
- 2001 - Giuseppe Sinopoli, Italian conductor and composer (b. 1946)
- 2002 - Alan Dale, American singer (b. 1925)
- 2002 - Pierre Rapsat, Belgian singer-songwriter (b. 1948)
- 2003 - Ruth Hale, American playwright and actress (b. 1908)
- 2003 – Daijiro Kato, Japanese motorcycle racer (b. 1976)
- 2003 – Bernard Katz, German biophysicist (b. 1911)
- 2005 - Zygfryd Blaut, Polish footballer (b. 1943)
- 2010 – Dorothy Height, American Civil Rights activist (b. 1912)
- 2011 - Journalists killed in Libya:
- 2014 - Rubin "Hurricane" Carter, American boxer (b. 1937)
- 2014 - Neville Wran, Australian politician, former Premier of New South Wales (b. 1926)
- 2014 - Benedikt Sarnov, Russian literary critic and writer (b. 1927)
- 2014 - Alistair MacLeod, Canadian writer and academic (b. 1936)
- 2015 - Frederic Morton, Austrian-American writer (b. 1924)
- 2015 - Aharon Lichtenstein, French-born American-Israeli rabbi (b. 1933)
- 2015 - Richard Anthony, Egyptian-born French singer (b. 1938)
- 2015 - Bob St. Clair, American football player (b. 1931)
- 2015 - Ibrahim Yusri, Egyptian actor (b. 1950)
- 2015 - Peter Howell, English actor (b. 1929)
- 2016 - Victoria Wood, English comedienne, actress and writer (b. 1953)
- 2016 - Guy Hamilton, English film director (b. 1922)
- 2016 - Avril Henry, English academic (b. 1934)
- 2016 - Leonie Kramer, Australian academic (b. 1924)
- 2016 - Harry Perkowski, American baseball player (b. 1922)
- 2017 - Germaine Mason, Jamaican-born British high jumper (b. 1983)
- 2017 - Jay Dickey, American politician (b. 1939)
- 2017 - Roberto Ferreiro, Argentine footballer (b. 1935)
- 2017 - Cuba Gooding, Sr., American singer (b. 1944)
- 2017 - Lawrence Hogan, American politician (b. 1928)
- 2017 - Magdalena Abakanowicz, Polish sculptor (b. 1930)
- 2018 - Avicii, Swedish DJ, musician and music producer (b. 1989)
- 2018 - Roy Bentley, English footballer (b. 1924)
- 2018 - Pedro Erquicia, Spanish journalist and television producer (b. 1943)
- 2018 - Rajinder Sachar, Pakistan-Indian political activist and judge (b. 1923)
- 2018 - Al Swift, American broadcaster and politician (b. 1935)
- 2018 - Shane Yarran, Australian rules footballer (b. 1989)
- 2018 - Charles Zwick, American civil servant (b. 1926)
- 2019 - Joe Armstrong, British computer scientist (b. 1950)
- 2019 - Reggie Cobb, American football player (b. 1968)
- 2019 - Monir Shahroudy Farmanfarmaian, Iranian artist (b. 1922)
- 2019 - Karl Grob, Swiss footballer (b. 1946)
- 2019 - Braulio Lara, Dominican baseball player (b. 1988)
- 2019 - David V. Picker, American film executive and producer (b. 1931)