|Covid-19|January 2 – U.S. Secretary of State John Hay announces the Open Door Policy to promote American trade with China.
January 5 – Dr. Henry A. Rowland of Johns Hopkins University announces a theory about the cause of the Earth's magnetism.
January 6 – Second Boer War: Boers attempt to end the Siege of Ladysmith, which leads to the Battle of Platrand.
January 9 – S.S. Lazio, an Italian professional sports club, is founded in Rome.
Puccini's opera Tosca premieres in Rome, Italy.
The U.S. Senate accepts the British-German treaty of 1899, in which the United Kingdom renounced its claims to the American Samoa portion of the Samoan Islands.
January 24 – The Second Boer War: At the Battle of Spion Kop, Boer troops defeat the British Army.
January 27 – Boxer Rebellion: Foreign diplomats in Peking, Qing dynasty China, demand that the Boxer rebels be disciplined.
January 31 – Datu Muhammad Salleh, leader of the Mat Salleh Rebellion in North Borneo, is shot dead in Tambunan.
February 5 – The United Kingdom and the United States sign a treaty for the building of a Central American shipping canal across Central America in Nicaragua.
February 6 – The international arbitration court at The Hague is created when the Netherlands' Senate ratifies an 1899 peace conference decree.
February 8 – Second Boer War: British troops are defeated by the Boers at Ladysmith.
February 14 – Second Boer War – Battle of Paardeberg: 20,000 British troops invade the Orange Free State.
February 15 – Second Boer War: The Siege of Kimberley is lifted.
February 17 – Second Boer War: Battle of Paardeberg: British troops defeat the Boers.
FC Bayern, Germany's most successful football club, is founded in Munich.
Second Boer War: British military leaders accept the unconditional notice of surrender from Boer General Piet Cronjé.
British Labor Party, officially established in London, England, United Kingdom.
March 5 – Two U.S. Navy cruisers are sent to Central America to protect American interests in a dispute between Nicaragua and Costa Rica.
March 6 – A coal mine explosion in West Virginia, U.S.A. kills 50 miners.
March 14 – Botanist Hugo de Vries rediscovers Mendel's Laws of Heredity.
March 15 – The Gold Standard Act is ratified, placing the United States currency on the gold standard.
March 16 – The British archaeologist Sir Arthur Evans purchases the land on Crete on which the ruins of the palace of Knossos stand. He begins to unearth some of the palace three days later.
March 18 – AFC Ajax, a most successful football club in Netherlands, founded in Amsterdam.
March 27 – The arrival of a Russian naval fleet in Korea causes concern to the Imperial Japanese government.
April 14 – The Paris World Exhibition opens.
April 22 – Battle of Kousséri: French forces secure their domination of Chad. Warlord Rabih az-Zubayr is defeated and killed.
May 1 – An explosion of blasting powder in a coal mine in Scofield, Utah kills 200.
May 14 – The second Modern Olympic Games opens in Paris (as part of the Paris World Exhibition).
Second Boer War: The British Army relieves the Siege of Mafeking.
Boxer Rebellion: Boxers destroy three villages near Peking and kill sixty Chinese Christians.
L. Frank Baum's The Wonderful Wizard of Oz is published in Chicago, the first of Baum's Oz books chronicling the fictional Land of Oz for children.
May 18 – The United Kingdom proclaims a protectorate over Tonga.
May 21 – Russia invades Manchuria.
May 24 – Second Boer War: The British annex the Orange Free State as the Orange River Colony.
May 28 – Boxer Rebellion: The Boxers attack Belgians in the Fengtai railway station.
May 29 – N'Djamena, the capital city of Chad, is founded as Fort-Lamy by French commander Émile Gentil.
May 31 – Boxer Rebellion: Peacekeepers from various European countries arrive in China where they join with Japanese forces.
June 1 – American temperance agitator Carrie Nation begins her crusade to demolish saloons.
June 5 – Second Boer War: British soldiers take Pretoria.
June 14 – The Reichstag approves a second law that allows the expansion of the Imperial German Navy
June 17 – Boxer Rebellion: Battle of Dagu Forts: Naval forces of the Eight-Nation Alliance capture the Taku Forts on the Hai River estuary in China.
June 20 – Boxer Rebellion: Boxers gather about 20,000 people near Peking and kill hundreds of European citizens, including the German ambassador.
June 25 – The Taoist monk Wang Yuanlu discovers the Dunhuang manuscripts in the Mogao Caves of Dunhuang, China, where they have been sealed since the early 11th century.
June 30 – Hoboken Docks fire: A wharf fire at the docks in Hoboken, New Jersey, owned by the North German Lloyd Steamship line spreads to German passenger ships Saale, Main, and Bremen. The fire engulfs the adjacent piers and nearby ships, killing 326 people.
July 2 – The first zeppelin flight is carried out over Lake Constance near Friedrichshafen, Germany.
July 12 – German cruise liner SS Deutschland breaks the record for the Blue Riband for the first time with an average speed of 22.4 knots (41.5 km/h).
July 23-25 – The First Pan-African Conference is held in London.
July 29 – King Umberto I of Italy is assassinated by the Italian-born anarchist Gaetano Bresci.
August 4 – Elizabeth Bowes-Lyon, later Queen Elizabeth The Queen Mother, was born in London
August 14 – Boxer Rebellion: An international contingent of troops, under British command, invades Peking and frees the Europeans taken hostage.
September 8 – The 1900 Galveston hurricane kills about 8,000 people.
September 12 ; Admiral Fredrik von Otter becomes Prime Minister of Sweden.
September 13 – Philippine–American War: Filipino resistance fighters defeat a detachment of American soldiers in the Battle of Pulang Lupa.
September 17 – Philippine–American War: Filipinos under Juan Cailles defeat the Americans under Colonel Benjamin F. Cheatham at the Battle of Mabitac.
November 29 – Herbert Kitchener succeeds Frederick Roberts as commander-in-chief of the British forces in South Africa and implements a scorched earth strategy.
December 14 – Max Planck announces his discovery of the law of black body emission, marking the birth of quantum physics.
December 27 – British human rights activist Emily Hobhouse arrives in Cape Town.
Australasian prospector Albert Fuller Ellis identifies phosphate deposits on the Pacific Islands of Nauru and Banaba Island (Ocean Island).
In New Haven, Connecticut, U.S., Louis Lassen of Louis' Lunch makes the first modern-day hamburger sandwich.
First Michelin Guide published in France.
Karl Landsteiner develops a system of blood grouping
Paola Borboni, Italian film actress (d. 1995)
Xavier Cugat, Cuban bandleader (d. 1990)
Roger Maxwell, English actor (d. 1971)
Lillian Rich, English silent film actress (d. 1954)
Chiune Sugihara, Japanese diplomat (d. 1986)
William Haines, American actor (d. 1973)
Mansaku Itami, Japanese film director, tuberculosis (d. 1946)
Maurice Jaubert, French composer, wounded in combat (d. 1940)
Ernst Neubach, Austrian screenwriter, producer, and director (d. 1968)
James Bond, American ornithologist (d. 1989)
William Young, British veteran of World War I (d. 2007)
George Magrill, American film actor (d. 1952)
Yves Tanguy, French painter (d. 1955)
January 6 – John Sinclair, American actor (d. 1945)
Dorothy Adams, American character actress (d. 1988)
François de Menthon, French politician and professor of law (d. 1984)
Emmanuel d'Astier de La Vigerie, French journalist and politician (d. 1969)
Richard Halliburton, American adventurer and writer (d. 1939)
January 10 – Jean Gehret, Swedish actor and director (d. 1956)
Borden Chase, American writer (d. 1971)
Lloyd French, American director, heart disease (d. 1950)
January 16 – Edith Frank, German-Dutch mother of Anne Frank (d. 1945)
January 18 – Wan Laiming, Chinese animator, (d. 1997)
January 22 – Ernst Busch, German singer and actor (d. 1980)
January 23 – William Ifor Jones, Welsh conductor and organist (d. 1988)
January 24 – Theodosius Dobzhansky, Ukrainian geneticist and evolutionary biologist (d. 1975)
January 26 – Karl Ristenpart, German conductor (d. 1967)
January 27 – Hyman Rickover, American admiral (d. 1986)
January 28 – Rajagopala Tondaiman, King of Pudukkottai (d. 1950)
January 30 – Martita Hunt, Argentine-born British actress (d. 1969)
February 2 – Józef Kowalski, Once Poland's oldest living man and one of the last veterans of the Polish–Soviet War (d. 2013)
February 4 – Jacques Prévert, French lyricist and author (d. 1977)
February 5 – Adlai Stevenson, American politician (d. 1965)
Hans-Georg Gadamer, German philosopher (d. 2002)
Jōsei Toda, Japanese educator and activist (d. 1958)
February 12 – Roger J. Traynor, American judge (d. 1983)
February 12 – Vasily Chuikov, Marshal of the Soviet Union during WWII (d. 1982)
Luis Buñuel, Spanish film director (d. 1983)
James Sisnett, Supercentenarian from Barbados (d. 2013)
February 25 – Richard M. Hollingshead, Jr., American inventor of the drive-in theatre (d. 1975)
February 28 – Wolfram Hirth, German pilot and aircraft designer (d. 1959)
March 4 – Herbert Biberman, American screenwriter and film director (d. 1971)
Lorimer Dods, Australian medical pioneer (d. 1981)
Fritz London, German-Jewish physicist (d. 1954)
March 8 – Howard Aiken, American computing pioneer (d. 1973)
March 10 – Violet Brown, Jamican supercentenarian, oldest Jamican ever
March 12 – Gustavo Rojas Pinilla, military President of Colombia (d. 1975)
March 13 – Giorgos Seferis, Greek poet, recipient of the Nobel Prize in Literature (d. 1971)
March 19 – Frédéric Joliot, French physicist, recipient of the Nobel Prize in Chemistry (d. 1958)
March 23 – Erich Fromm, German-born psychologist and philosopher (d. 1980)
John McEwen, Prime Minister of Australia (d. 1980)
Oscar Elton Sette, American fisheries scientist (d. 1972)
March 31 – Prince Henry, Duke of Gloucester (d. 1974)
April 1 – Stefanie Clausen, Danish diver (d. 1981)
April 2 – Roberto Arlt, Argentine writer (d. 1942)
Albert Ingham, English mathematician (d. 1967)
Albert Walsh, Lieutenant Governor of Newfoundland (d. 1958)
April 5 – Spencer Tracy, American actor (d. 1967)
April 8 – Marie Byles, Australian solicitor (d. 1979)
April 16 – Polly Adler, Russian author (d. 1962)
April 21 – Hans Fritzsche, German Nazi official (d. 1953)
April 24 – Elizabeth Goudge, English writer (d. 1984)
April 25 – Wolfgang Pauli, Austrian-born physicist, Nobel Prize laureate (d. 1958)
April 26 – Charles Richter, American geophysicist and inventor (d. 1985)
April 27 – August Koern, Estonian statesman and diplomat (d. 1989)
April 28 – Maurice Thorez, French Communist Leader (d. 1964)
April 30 – Cecily Lefort, English World War II heroine (d. 1945)
May 1 – Ignazio Silone, Italian author (d. 1978)
May 2 – A. W. Lawrence, British leading authority on classical sculpture and architecture (d. 1991)
May 6 – Zheng Ji, Chinese nutritionist and biochemist (d. 2010)
May 11 – Thomas H. Robbins, Jr., American admiral (d. 1972)
May 12 – Helene Weigel, Austrian actress (d. 1971)
May 23 – Hans Frank, German Nazi official (d. 1946)
May 27 – Uładzimir Žyłka, Belarusian poet (d. 1933)
May 28 – Tommy Ladnier, American jazz trumpeter (d. 1939)
May 29 – David Maxwell Fyfe, 1st Earl of Kilmuir, British politician, lawyer, and judge (d. 1967)
Rolland Fisher, American temperance activist (d. 1982)
Leo Picard, German-born Israeli geologist (d. 1997)
June 4 – George Watkins, American baseball player (d. 1970)
June 5 – Dennis Gabor, Hungarian physicist, Nobel Prize laureate (d. 1979)
June 7 – Glen Gray, American saxophonist (d. 1963)
June 11 – Leopoldo Marechal, Argentine writer (d. 1970)
June 15 – Paul Mares, American jazz trumpeter (d. 1949)
June 17 – Martin Bormann, German Nazi official (d. 1945)
June 21 – Choi Yong-kun, North Korean general and defense minister (d. 1976)
Juan Carlos Caballero Vega, Mexican revolutionary (d. 2010)
Raphael Lemkin, Polish-born international lawyer (d. 1959)
Philip D'Arcy Hart, British medical researcher and pioneer in tuberculosis treatment (d. 2006)
Louis Mountbatten, 1st Earl Mountbatten of Burma, born Prince Louis of Battenberg, English naval officer and last Viceroy of India (d. 1979)
June 29 – Antoine de Saint-Exupéry, French pilot and writer (d. 1944)
June 30 – Alf Ihlen, Norwegian industrialist (d. 2006)
July 4 – Robert Desnos, French poet (d. 1945)
July 5 – Richard K. Webel, American landscape architect (d. 2000)
July 6 – Frederica Sagor Maas, American playwright, essayist, and author (d. 2012)
July 13 – George Lewis, American jazz clarinetist (d. 1968)
July 23 – John Babcock, last surviving World War I veteran of the Canadian military (d. 2010)
July 29 – Eyvind Johnson, Swedish writer, Nobel Prize laureate (d. 1976)
August 3 – Ernie Pyle, American journalist (d. 1945)
Arturo Umberto Illia, 34th President of Argentina (d. 1983)
Elizabeth Bowes-Lyon (later Queen Elizabeth The Queen Mother, queen consort of George VI; d. 2002)
Nabi Tajima, Japanese supercentenarian
August 6 – Cecil H. Green, British-born geophysicist and businessman (d. 2003)
August 8 – Alexis Minotis, Greek actor and stage director (d. 1990)
August 10 – Arthur Espie Porritt, New Zealand politician and athlete (d. 1994)
Philip Phillips, American archaeologist (d. 1994)
Alexander Mosolov, Russian composer (d. 1973)
August 18 – Glenn Albert Black, American archaeologist (d. 1964)
Colleen Moore, American actress (d. 1988)
Gilbert Ryle, British philosopher (d. 1976)
August 22 – Sergey Ozhegov, Russian lexicographer (d. 1964)
August 23 – Ernst Krenek, Austrian-American composer (d. 1991)
August 25 – Sir Hans Adolf Krebs, German physician and biochemist, recipient of the Nobel Prize in Physiology or Medicine (d. 1981)
August 26 – Hellmuth Walter, German engineer and inventor (d. 1980)
September 3 – Urho Kekkonen, President of Finland (d. 1986)
September 6 – W. A. C. Bennett, Canadian politician (d. 1979)
September 11– Jimmy Brain, English footballer (d. 1971)
September 12 – Eric Thiman, English composer (d. 1975)
September 18 – Thomas Darden, American rear admiral, 37th Governor of American Samoa (d. 1961)
September 20 – Uuno Klami, Finnish composer (d. 1961)
September 22 – Paul Hugh Emmett, American chemical engineer (d. 1985)
September 23 – Louise Nevelson, Ukrainian-born American sculptor (d. 1988)
Miguel Alemán Valdés, President of Mexico (d. 1983)
Auguste van Pels, German-Dutch mother of Peter van Pels, housemate of Anne Frank (d. 1945)
October 1 – Tom Goddard, English cricketer (d. 1966)
October 6 – Stan Nichols, English cricketer (d. 1961)
October 7 – Heinrich Himmler, German Nazi official and SS head (d. 1945)
Frederick Moosbrugger, American admiral (d. 1974)
Frank O'Grady, Australian public servant (d. 1981)
October 10 – Helen Hayes, American actress (d. 1993)
October 16 – Edward Ardizzone, English painter, printmaker and author (d. 1979)
October 17 – Jean Arthur, American actress (d. 1991)
October 19 – Bill Ponsford, Australian cricketer (d. 1991)
October 30 – Ragnar Granit, Finnish neuroscientist, recipient of the Nobel Prize in Physiology or Medicine (d. 1991)
November 4 – Lucrețiu Pătrășcanu, Romanian communist activist and sociologist (d. 1954)
Martin Dies, Jr., American politician (d. 1972)
Natalie Schafer, American actress (d. 1991)
November 6 – Hugh Prosser, American actor (d. 1952)
Charley Paddock, American athlete (d. 1943)
Margaret Mitchell, American writer (Gone With The Wind) (d. 1949)
Halina Konopacka, Polish athlete (d. 1989)
Frederick Lawton, 9th Director of the Office of Management and Budget (d. 1975)
November 13 – David Marshall Williams, American inventor (d. 1975)
November 14 – Aaron Copland, American composer (d. 1990)
November 16 – Nikolai Pogodin, Soviet playwright (d. 1962)
November 22 – Tom Macdonald, Welsh journalist and novelist (d. 1980)
November 25 – Rudolf Höß, German Nazi official (d. 1947)
November 29 – Hakan Malmrot, Swedish swimmer (d. 1987)
Ulrich Inderbinen, Swiss mountain guide (d. 2004)
Richard Kuhn, Austrian chemist, Nobel Prize laureate (d. 1967)
December 4 – John Axon, British railwayman (d. 1957)
December 6 – Agnes Moorehead, American actress (Bewitched) (d. 1974)
December 7 – Christian Matras, Faroese linguist and poet (d. 1988)
December 10 – Dominic Costa, Australian politician (d. 1976)
December 12 – Sammy Davis, Sr., American dancer (d. 1988)
December 16 – Rudolf Diels, German Nazi civil servant and Gestapo chief (d. 1957)
December 20 – Marinus van der Goes van Naters, Dutch politician (d. 2005)
December 24 – Joey Smallwood, former premier of Newfoundland (d. 1991)
December 25 – Antoni Zygmund, Polish mathematician (d. 1992)
Virginia Frances Sterrett, American artist and illustrator (d. 1931)
Yung Fung-shee, Hong Kong philanthropist (d. 1972)
René Pellos, French artist (d. 1998)
Luigi Stipa, Italian aeronautical, hydraulic, and civil engineer and aircraft designer (d. 1992)
Harold Tamblyn-Watts, British cartoonist (d. 1999)
January 5 – William A. Hammond, American military physician and neurologist, eleventh Surgeon General of the United States Army (1862–1864) (b. 1828)
January 20 – John Ruskin, English writer and social critic (b. 1819)
January 31 – John Douglas, 9th Marquess of Queensberry, Scottish nobleman and boxer (b. 1844)
February 18 – Clinton L. Merriam, American politician (b. 1824)
February 23 – William Butterfield, British architect (b. 1814)
Gottlieb Daimler, German inventor and automotive pioneer (b. 1834)
Carl Bechstein, German piano maker (b. 1826)
March 10 – Johan Peter Emilius Hartmann, Danish composer (b. 1805)
March 18 – Hjalmar Kiærskou, Danish botanist (b. 1835)
March 28 – Piet Joubert, Boer politician and military commander (b. 1834)
March 29 – Cyrus K. Holliday, cofounder of Topeka, Kansas, and first president of the Atchison, Topeka and Santa Fe Railway (b. 1826)
Joseph Louis François Bertrand, French mathematician (b. 1822)
Osman Nuri Pasha, Ottoman military leader (b. 1832)
April 12 – James Richard Cocke, American physician, homeopath, and a pioneer hypnotherapist (b. 1863)
April 17 – George Curry, Wild West robber (Wild Bunch) (shot) (b. 1871)
April 19 – James Dawson, Australian activist (b. 1806)
April 22 – Amédée-François Lamy, French soldier (b. 1858) (killed in battle)
April 24 – George Campbell, 8th Duke of Argyll, British politician (b.1823)
April 30 – Casey Jones, American railway engineer (b. 1863)
May 1 – Mihály Munkácsy, Hungarian painter (b. 1844)
May 9 – Carit Etlar (Carl Brosbøll), Danish author (b. 1816)
May 18 – Félix Ravaisson-Mollien, French philosopher (b. 1813)
Samori Ture, West African empire-builder (b. 1830)
Clarence Cook, American critic and writer (b. 1828)
June 3 – Mary Kingsley, English explorer and writer (b. 1862)
June 5 – Stephen Crane, American author (b. 1871)
June 11 – Belle Boyd, American Confederate spy and actress (b. 1843)
June 19 – Princess Josephine of Baden (b. 1813)
July 5 – Henry Barnard, American educationalist (b. 1811)
July 8 – Henry D. Cogswell, American philanthropist (b. 1820)
July 29 – Umberto I, King of Italy (assassinated) (b. 1844)
July 31 – Alfred, Duke of Saxe-Coburg and Gotha, second son of Queen Victoria (b. 1844)
August 1 – Rafael Molina Sanchez, Spanish bullfighter (b. 1841)
August 4 – Étienne Lenoir, Belgian engineer (b. 1822)
August 7 – Wilhelm Liebknecht, German Social Democratic politician (b. 1826)
August 10 – Charles Russell, Baron Russell of Killowen, Lord Chief Justice of England (b. 1832)
August 12 – Wilhelm Steinitz, Austrian-born chess player, first unsesputed World Champion (b. 1836)
August 13 – Vladimir Solovyov, Russian philosopher and poet (b. 1853)
August 16 – José Maria de Eça de Queirós, Portuguese writer (b. 1845)
August 23 – Kuroda Kiyotaka, Prime Minister of Japan (b. 1840)
August 25 – Friedrich Nietzsche, German philosopher and writer (b. 1844)
William Marsh Rice, American philanthropist and university founder (b. 1816)
Arsenio Martínez-Campos y Antón, Spanish revolutionary (b. 1831)
September 27 – Albert Bernhard Frank, German botanist and mycologist (b. 1839)
September 29 – Samuel Fenton Cary, American politician (b. 1814)
October 15 – Zdeněk Fibich, Czech composer (b. 1850)
October 20 – Charles Dudley Warner, American writer (b. 1829)
October 22 – John Sherman, American politician (b.1823)
October 28 – Max Müller, German philologist and Orientalist (b. 1823)
November 22 – Sir Arthur Sullivan. English composer (b. 1842)
November 30 – Oscar Wilde, Irish writer (b. 1854)
December 4 – Aquileo Parra, 11th President of Colombia (b. 1825)
December 14 – Paddy Ryan, Irish American boxer, former world's heavyweight champion (b. 1851)
December 21 – Leonhard Graf von Blumenthal, Prussian field marshal (b. 1810)
undated - Lin Hei'er, Chinese rebel
World population: 1,640,000,000
Japan: c. 45,000,000
Latin America: 74,000,000
Northern America: 82,000,000
1900 (MCM) was an exceptional common year starting on Monday (dominical letter G) of the Gregorian calendar and a leap year starting on Saturday (dominical letter BA) of the Julian calendar, the 1900th year of the Common Era (CE) and Anno Domini (AD) designations, the 900th year of the 2nd millennium, the 100th and last year of the 19th century, and the 1st year of the 1900s decade. As of the start of 1900, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923. As of March 1 (O.S. February 17), when the Julian calendar acknowledged a leap day and the Gregorian calendar did not, the Julian calendar fell one day further behind, bringing the difference to 13 days.