1917 1918 1919 - 1920 - 1921 1922 1923
| Decades: |
1890s 1900s 1910s - 1920s - 1930s 1940s 1950s
- January 1 - Babe Ruth is traded by the Boston Red Sox to the New York Yankees for $125,000, the largest sum ever paid for a player at that time.
- January 7 - Forces of Russian White admiral Kolchak surrender in Krasnoyarsk. The Great Siberian Ice March ensues.
- January 9
- January 16
- Prohibition begins in the United States with the Eighteenth Amendment to the Constitution coming into effect.
- The World War I Allies demand that the Netherlands extradite the German Kaiser Wilhelm II, who has fled there.
- Zeta Phi Beta Sorority, Incorporated, was founded on the campus of Howard University in Washington D.C.
- January 19 - The United States Senate votes against joining the League of Nations.
- January 22 - The Australian Country Party is officially formed.Matthew soares
- January 23 - The Netherlands refuses to extradite the German Kaiser.
- January 28 - The Spanish legion is founded and stationed in North Africa to fight rebels in Morocco.
- January 28 - Turkey gives up the Ottoman Empire and all non-Turkish areas.
- January 30 - Oldest surviving pro wrestling match on film happened on this day with Joe Stecher defeating Earl Caddock
- February 1 - The Royal Canadian Mounted Police begin operations.
- February 2
- February 7 - Admiral Kolchak and Viktor Pepelyayev are executed by firing squad near Irkutsk.
- February 9 - League of Nations gives Spitsbergen to Norway.
- February 10 - Jozef Haller de Hallenburg performs the symbolic wedding of Poland to the sea, celebrating restitution of Polish access to open sea.
- February 14 - The League of Women Voters is founded in Chicago.
- February 17 -A woman named Anna Anderson tries to commit suicide in Berlin and is taken to mental hospital, where she claims she is Anastasia.
- February 22 - In Emeryville, California, the first dog racing track to employ an imitation rabbit opens.
- February 24 - Adolf Hitler presents his National Socialist program in Munich.
- March - World's first peaceful establishment of a social democratic government takes place in Sweden. Hjalmar Branting takes over when Nils Edén resigns.
- March 1
- March 13-March 17 - Wolfgang Kapp fails in his coup attempt in Germany due to public resistance and a general strike.
- March 15 - Red Army of Ruhr, communist army 60.000 men strong, formed
- March 19 - US Congress refuses to ratify Versailles Treaty.
- March 23 - Admiral Horthy declares that Hungary is a monarchy without anyone on the throne.
- March 26
- March 28 - The Palm Sunday tornado outbreak of 1920 hits the Great Lakes region and Deep South states.
- March 29 - Sir William Robertson, who enlisted in 1877, becomes a field marshal in the British Army, the first man to rise to this rank from private
- March 31 - Government of Ireland Act 1920 is presented in British parliament.
- April 2 - German army marches to Ruhr to fight Red Ruhr Army.
- April 4 - Jerusalem pogrom of April, 1920 . Violence between Arabic and Jewish resident in Jerusalem . governor declares the state of siege
- April 6 - The short-lived Far Eastern Republic declared in eastern Siberia
- April 11 - Mexican Revolution - Álvaro Obregón flees from Mexico City during a trial intended to ruin his reputation - he flees to Guerrero where he joins Fortunato Maycotte
- April 19 - Germany and Bolshevist Russia agree to the exchange of prisoners of war.
- April 20 - Álvaro Obregón announces in Chilpancingo that he intends to fight against the rule of Venustiano Carranza
- April 23 - National council in Turkey denounces the government of sultan Mehmed VI and announces a temporary constitution.
- April 24 - Polish-Soviet War: Polish and Anti-Soviet Ukrainian troops attack the Red Army in Soviet Ukraine.
- April 26 - the Khorezm People's Soviet Republic is officially created by Bolshevist Russia as the successor to the Khanate of Khiva.
- May 2 - The first game of the Negro National League baseball is played in Indianapolis, Indiana.
- May 7
- Polish-Soviet War: Polish troops occupy Kyiv. The government of Ukrainian People's Republic returns to the city.
- Venustiano Carranza leaves Mexico City in a large train.
- Treaty of Moscow (1920): Soviet Russia recognizes independence of the Democratic Republic of Georgia only to invade the country six months later.
- May 9 - Álvaro Obregón's troops enter Mexico City
- May 15 - Maria Bochkareva executed in Soviet Russia
- May 16 -
- Joan of Arc is canonised. Over 30,000 people attended the ceremony in Rome, including 140 descendants of Joan of Arc's family. Pope Benedict XV presided over the rite, for which the interior of St. Peter's Basilica in Rome was richly decorated.
- Referendum in Switzerland is favorable to joining League of Nations.
- May 17
- May 20 - Venustiano Carranza arrives in San Antonio Tlaxcalantongo. Troops of Rodolfo Herrera attack him at night and shoot him
- May 24 - Venustiano Carranza is buried in Mexico City - all of his mourning allies are arrested. Adolfo de la Huerta is elected provisional president
- May 27 - Tomáš Masaryk becomes president of Czechoslovakia.
- May 29 - Great Horncastle flood. 20 people killed.
- June 4 - Treaty of Trianon, Treaty of Peace between The Allied and Hungary.
- June 12 - Polish-Soviet War: Red Army retakes Kyiv.
- June 13 - The United States Postal Service rules that children may not be sent via parcel post
- June 15 - New border treaty between Germany and Denmark gives northern Schleswig to Denmark.
- June 22 - Greece attacks Turkish troops.
- July 1 - Germany declares its neutrality in the war between Poland and Soviet Russia
- July 2 - Polish-Soviet War: Red Army continues offensive into Poland.
- July 10 - Arthur Meighen becomes Canada's ninth prime minister.
- July 12 - Bolshevist Russia recognizes independent Lithuania.
- July 13 - London County Council bars foreigners from council jobs.
- July 14 - France declares that Faisal I of Syria is deposed and occupies Damascus and Aleppo.
- July 19 – August 7 – The Second Congress of the Communist International took place in St. Petersburg and Moscow. The notorious Twenty-one Conditions were adopted.
- July 22 - Polish-Soviet War: Poland sues for peace with Bolshevist Russia.
- July 23 - The French defeat the Syrian army in the Battle of Maysalun.
- July 25 - First transatlantic two-way radio broadcast?
- July 26 - Pancho Villa takes over Sabina and contacts de la Huerta to offer his conditional surrender. He signs his surrender in July 28
- July 29 - The United States Bureau of Reclamation begins construction of the Link River Dam as part of the Klamath Reclamation Project.
- July 31 - France prohibits the sale or prescription of contraceptives.
- August 2 - British parliament passes bill to restore order in Ireland, suspending jury trials.
- August 3 - Catholics riot in Belfast.
- August 10 - Ottoman sultan Mehmed VI's representatives sign the Treaty of Sèvres.
- August 11 - Bolshevik Russia recognizes independent Estonia and Latvia.
- August 13 - August 25 - Polish-Soviet War: The Red Army is defeated in the Battle of Warsaw.
- August 15 - Town Hall of Templemore, Ireland, is burned down during the riots.
- August 18 - Amendment 19 allowed women the right to vote under constitutional protection.
- August 19-August 25 - Second Silesian Uprising, the Poles in Upper Silesia rise against the Germans
- August 20 - The first commercial radio station in the United States, 8MK (WWJ), begins operations in Detroit, Michigan.
- August 26 - 19th Amendment to US constitution is passed, guaranteeing women's suffrage.
- September 4 - El Tercio de Extranjeros, the "Regiment of Foreigners" (modern-day Spanish Legion) inaugurated in Spain
- September 5 - Presidential elections begin in Mexico
- September 8 - Gabriele D'Annunzio proclaims the Italian Regency of Carnaro in the city of Fiume.
- September 16 - The Wall Street bombing: a hi cordell bomb in a horse wagon explodes in front of the J.P.Morgan building in New York City - 38 dead, 400 injured
- September 20 - The first soldier joins the Spanish Legion.
- September 22 - Flying Squad formed in London Metropolitan Police.
- September 29
- October 9 - Polish troops take Vilnius
- October 10 - In the Carinthian Plebiscite a large part of Carinthia Province votes to become part of Austria rather than of the Yugoslavia.
- October 12 - Polish-Soviet War After Polish army captures Tarnopol, Dubno, Minsk, and Dryssa, the ceasefire is enforced.
- October 18 - Thousands of unemployed demonstrate in London ? 50 injured
- October 26 - Álvaro Obregón is announced elected president of Mexico
- October 27 - League of Nations moves its headquarters to Geneva, Switzerland
- November 2
- Warren G. Harding defeats James M. Cox and Eugene V. Debs in the U.S. presidential election, the first national U.S. election in which women have the right to vote.
- In the United States, KDKA AM of Pittsburgh, Pennsylvania (owned by Westinghouse) starts broadcasting as a commercial radio station. The first broadcast was the results of the U.S. presidential election, 1920.
- November 11 - Unknown Soldier buried in Westminster Abbey.
- November 15 - In Geneva, the first assembly of the League of Nations is held.
- November 16 - Queensland and Northern Territory Aviation Services (Qantas) is founded by Hudson Fysh and Paul McGinniss.
- November 17 - The council of the League of Nations accepts the constitution for the Free City of Danzig.
- November 21 - Bloody Sunday - British forces open fire on spectators and players during a football match in Dublin's Croke Park, killing 14 Irish civilians. This followed the assassinations of 12 British agents by the IRA in an earlier attack elsewhere.
- November 28 - The Third Cork Brigade Flying Column under Tom Barry successfully ambush two lorries of British soldiers at Kilmichael, County Cork, in the Kilmichael Ambush
- Edmonton Symphony Orchestra's first concert
- December 5 - Referendum in Greece is favorable to reinstatement of monarchy.
- December 11 - Martial law in Ireland.
- December 16
- December 22 - The 8th Congress of Soviets of the Russian SFSR adopts GOELRO plan, the major plan of the economical development of the country.
- December 23 - United Kingdom and France ratify the border between French-held Syria and British-held Palestine.
- December 25 - Foundation of The Rosicrucian Fellowship's Spiritual Healing Temple "The Ecclesia" at Mount Ecclesia, Oceanside, California (United States).
- January 6 - Sun Myung Moon, founder of the Unification Church (d. 2012)
- March 4 - Bryant W. Bowles - American white resistance leader and founder of the 1950s NAAWP (d. 1997)
- March 28 - Frank L. Britton, anti-communist author (d. 2010)
- April 3 - John Demjanjuk, Ukrainian-born American auto worker, accused WW II war criminal (d. 2012)
- May 18 - Pope John Paul II (d. 2005)
- July 11 - James von Brunn, Holocaust Museum shooting suspect (d. 2010)
- August 22 - Ray Bradbury, American writer (d. 2012)
- September 10 - Dale H. Maple, US private accused of treason (d. 2001)
- November 9 - Byron de la Beckwith, Ku Klux Klan assassin, (d. 2001)