1936 1937 1938 - 1939 - 1940 1941 1942
| Decades: |
1900s 1910s 1920s - 1930s - 1940s 1950s 1960s
- January 5 – Amelia Earhart is officially declared dead after her disappearance.
- January 6 – Naturwissenschaften publishes evidence that nuclear fission has been achieved by Otto Hahn.
- January 13 – Black Friday: 71 people die across Victoria in one of Australia's worst ever bushfires.
- January 23 – “Dutch War Scare”: Admiral Wilhelm Canaris of the Abwehr leaks misinformation to the effect that Germany plans to invade the Netherlands in February, with the aim of using Dutch air-fields to launch a strategic bombing offensive against Britain. The “Dutch War Scare” leads to a major change in British policies towards Europe.
- January 24 – An earthquake kills 30,000 in Chile, and razes about 50000 sqmi.
- January 26 – Spanish Civil War: Spanish Nationalist troops, aided by Italy, take Barcelona.
- January 26 – In Paris, French Foreign Minister Georges Bonnet, in response to rumours (which are true) that he is seeking to end the French alliance system in Eastern Europe, gives a speech highlighting his government's commitment to the cordon sanitaire.
- January 27 – Adolf Hitler orders Plan Z, a 5-year naval expansion programme intended to provide for a huge German fleet capable of crushing the Royal Navy by 1944. The Kriegsmarine is given the first priority on the allotment of German economic resources.
- January 30 – Hitler gives a speech before the Reichstag calling for an "export battle" to increase German foreign exchange holdings. The same speech also sees Hitler's “prophecy” where he warns that if "Jewish financers" start a war against Germany, the "...result will be the annihilation of the Jewish race in Europe".
- February 2 – Hungary joins the Anti-Comintern Pact.
- February 6 – British Prime Minister Neville Chamberlain states in the House of Commons that any German attack on France will be automatically considered an attack on Britain.
- February 6 – In a response to Georges Bonnet's speech of January 26, German Foreign Minister Joachim von Ribbentrop, referring to Bonnet’s alleged statement of December 6, 1938 accepting Eastern Europe as being in Germany’s exclusive sphere of influence, protests that all French security commitments in that region are “now off limits”.
- February 10 – Spanish Nationalists complete their offensive in Catalonia.
- February 21 – The Golden Gate International Exposition opens in San Francisco, California.
- February 27 – The United Kingdom and France recognize Franco's government.
- February 27 – Borley Rectory in England burns.
- February 27 – Sit-down strikes are outlawed by the Supreme Court of the United States.
- March – The 1936-1939 Arab revolt in Palestine ends.
- March 1 – A Japanese Imperial Army ammunition dump explosion on the outskirts of Osaka kills 94.
- March 2 – Pope Pius XII (Cardinal Pacelli) succeeds Pope Pius XI as the 260th pope.
- March 3 – In Bombay, Mohandas Gandhi begins to fast in protest of the autocratic rule in India.
- March 13 – Hitler advises Jozef Tiso to declare Slovakia's independence in order to prevent its partition by Hungary and Poland.
- March 14 – The Slovak provincial assembly proclaims independence; priest Jozef Tiso becomes the president of the independent Slovak government.
- March 15 – German troops occupy the remaining part of Bohemia and Moravia; Czechoslovakia ceases to exist. The Ruthenian region of Czechoslovakia declares independence as Carpatho-Ukraine.
- March 16 – Princess Fawzia of Egypt marries Shah Mohammad Reza Pahlavi of Iran.
- March 16 – Hungary invades Carpatho-Ukraine; final resistance ends on March 18.
- March 17 – British Prime Minister Neville Chamberlain gives a speech in Birmingham, stating that Britain will oppose any effort at world domination on the part of Germany.
- March 18 – “Romanian War Scare”: Virgil Tilea, the Romanian Minister in London, spreads false rumours that Romania is on the verge of a German attack.
- March 20 – At an emergency meeting in London to deal with the Romanian crisis, French Foreign Minister Georges Bonnet suggests to Lord Halifax that the ideal state for saving Romania from a German attack is Poland.
- March 23 – The Slovak-Hungarian War begins.
- March 28 – Dictator Francisco Franco assumes power in Madrid.
- March 28 – American adventurer Richard Halliburton delivers a last message from a Chinese junk, before he disappears on a voyage across the Pacific Ocean.
- March 31 – Neville Chamberlain gives a speech in the House of Commons offering the British "guarantee" of the independence of Poland.
- April 1 – The Spanish Civil War comes to an end when the last of the Republican forces surrender.
- April 3 – Adolf Hitler orders the German military to start planning for Fall Weiss, the codename for the invasion of Poland.
- April 4 – Faisal II becomes King of Iraq.
- April 4 – The Slovak-Hungarian War ends with Slovakia ceding eastern territories to Hungary.
- April 7 – Italy invades Albania; King Zog flees.
- April 11 – Hungary leaves the League of Nations.
- April 13 – Britain offers a "guarantee" to Romania and Greece.
- April 14 – John Steinbeck's novel The Grapes of Wrath is first published.
- April 14 – At a meeting in Paris, French Foreign Minister Georges Bonnet meets with Soviet Ambassador Jakob Suritz, and suggests that a “peace front” comprising France, the Soviet Union, Great Britain, Poland and Romania would deter Germany from war.
- April 18 – The Soviet Union proposes a "peace front" to resist aggression.
- April 28 – In a speech before the Reichstag, Adolf Hitler renounces the Anglo-German Naval Agreement and the German–Polish Non-Aggression Pact.
- April 30 – The 1939 New York World's Fair opens.
- May 3
- May 7 – Spain leaves the League of Nations.
- May 17
- King George VI and Queen Elizabeth arrive in Quebec City to begin the first-ever tour of Canada by Canada's monarch.
- The British government issues the White Paper of 1939, sharply restricting Jewish immigration to the Palestine Mandate.
- Sweden, Norway, and Finland refuse Germany's offer of non-aggression pacts.
- May 20 – Pan-American Airways begins trans-Atlantic mail service with the inaugural flight of its Yankee Clipper from Port Washington, New York.
- May 22 – Germany and Italy sign the Pact of Steel.
- June 12 – The National Baseball Hall of Fame and Museum is officially dedicated in Cooperstown, New York.
- June 14 – Tientsin Incident: The Japanese blockade the British concession in Tianjin, China, beginning a crisis which almost causes an Anglo-Japanese war in the summer of 1939.
- June 17 – In the last public guillotining in France, murderer Eugen Weidmann is decapitated by the guillotine.
- June 23 – Talks are completed in Ankara between French Ambassador René Massigli and Turkish Foreign Minister Şükrü Saracoğlu, resolving the Hatay dispute in Turkey's favor. Turkey annexes Hatay.
- June 24 – The government of Siam changes its name to Thailand, which means 'Free Land'.
- July 2 – The 1st World Science Fiction Convention opens in New York City.
- July 4 – Lou Gehrig gives his last public speech, following his diagnosis of amyotrophic lateral sclerosis (ALS). In it, he states, "Today, I consider myself the luckiest man on the face of the earth."
- July 6 – The last remaining Jewish enterprises in Germany are closed.
- July 23 – Mahatma Gandhi the spiritual leader from India writes a personal letter to Adolf Hitler addressing him "My friend", requesting to prevent any possible war.
- August 2 – Albert Einstein writes President Franklin Roosevelt about developing the atomic bomb using uranium. This leads to the creation of the Manhattan Project.
- August 20 – Armored forces under the command of Soviet General Georgi Zhukov deliver a decisive defeat to Japanese Imperial Army forces in the Japanese-Soviet border war in Inner Mongolia.
- August 23 – Molotov-Ribbentrop Pact: Hitler and Stalin agree to divide Europe between themselves (Finland, Estonia, Latvia and eastern Poland to the USSR; Lithuania and western Poland to Germany).
- August 25 – Adolf Hitler postpones Fall Weiss for 5 days, due to a message from Benito Mussolini that he will not honor the Pact of Steel if Germany attacks Poland in 1939, and to the failure of Chamberlain's government to fall because of the German-Soviet Non-Aggression Pact.
- August 25 – An IRA bomb explodes in the centre of Coventry, England, killing 5 people.
- August 26 – The Kriegsmarine orders all German-flagged merchant ships to head to German ports immediately in anticipation of the invasion of Poland.
- August 27 – A Heinkel 178, the first turbojet-powered aircraft, flies for the first time with Captain Erich Warsitz in command.
- August 30 – Poland begins a mobilization against Germany.
- September 1 – World War II: Germany invades Poland, beginning World War II in Europe.
- September 1 – World War II: The German navy fires on Danzig.
- September 1 – World War II: Norway, Finland, Sweden, and Switzerland declare their neutrality.
- September 2 – World War II: Following the invasion of Poland, Danzig (now Gdańsk, Poland) is annexed to Germany.
- September 2 – World War II: Spain and Ireland declare their neutrality.
- September 3 – World War II: The United Kingdom, France, New Zealand and Australia declare war on Germany.
- September 4 – World War II: Nepal declares war on Germany.
- September 5 – World War II: The United States declares its neutrality in the war.
- September 6 – World War II: South Africa declares war on Germany.
- September 10 – World War II: Canada declares war on Germany.
- September 16 – A ceasefire ends the undeclared Border War between The Soviet Union (and Mongolian allies) and Japan.
- September 17 – World War II: The Soviet Union invades Poland and then occupies eastern Polish territories.
- September 21 – Radio station WJSV in Washington, D.C. records an entire broadcast day for preservation in the National Archives.
- September 22 – World War II: Joint victory parade of Wehrmacht and Red Army in Brest-Litovsk at the end of the Invasion of Poland.
- September 28 – World War II: Germany and the Soviet Union agree on a division of Poland after their invasion.
- September 28 – World War II: Warsaw surrenders to Germany; Modlin surrenders a day later; the last Polish large operational unit surrenders near Kock 8 days later.
- October 8 – World War II: Germany annexes Western Poland.
- October 11 – Manhattan Project: U.S. President Franklin D. Roosevelt is presented a letter signed by Albert Einstein, urging the United States to rapidly develop the atomic bomb.
- October 12 – Jüri Uluots becomes prime minister of Estonia.
- October 14 – The German U-Boat U-47 sinks the British battleship HMS Royal Oak.
- October 15 – The New York Municipal Airport (later renamed La Guardia Airport) is dedicated.
- November 4 – World War II: U.S. President Franklin D. Roosevelt orders the United States Customs Service to implement the Neutrality Act of 1939, allowing cash-and-carry purchases of weapons to non-belligerent nations.
- November 8 – Venlo Incident: Two British agents of SIS are captured by the Germans.
- November 8 – In Munich, Adolf Hitler narrowly escapes an assassination attempt by Georg Elser while celebrating the 16th anniversary of the Munich Putsch.
- November 15 – In Washington, D.C., U.S. President Franklin D. Roosevelt lays the cornerstone of the Jefferson Memorial.
- November 16 – Al Capone is released from Alcatraz.
- November 30 – Winter War: Soviet forces attack Finland and reach the Mannerheim Line, starting the war.
- November 30 – Sweden declares non-belligerency in the Winter War.
- December 2 – La Guardia Airport opens for business in New York City.
- December 12 – World War II HMS Duchess sinks after a collision with HMS Barham off the coast of Scotland with the loss of 124 men.
- December 13 – World War II – Battle of the River Plate: The German pocket battleship, Admiral Graf Spee is trapped by cruisers HMS Ajax, HMNZS Achilles, and HMS Exeter after a running battle off the coast of Uruguay. Admiral Graf Spee is scuttled by its crew off Montevideo harbor on December 17.
- December 14 – The League of Nations expels the USSR for attacking Finland.
- December 15 – The film Gone with the Wind, starring Vivien Leigh, Clark Gable, Olivia de Havilland and Leslie Howard, premieres at Loew's Grand Theatre in Atlanta, Georgia. It is based on Margaret Mitchell's best-selling novel. It is the longest American film made up to that time (nearly four hours).
- December 26 – Miners strike in Borinage, Belgium.
- December 27 – The 1939 Erzincan earthquake in Eastern Anatolia, Turkey, kills 30,000.
- October 18 - Lee Harvey Oswald, American assassin of John F. Kennedy (d. 1963)
- December 11 - Tom Hayden, New Left activist
- February 10 - Pope Pius XI (b. 1857)
- March 2 - Howard Carter, British archaeologist (b. 1874)
- September 23 - Sigmund Freud, Austrian psychiatrist (b. 1856)
- September 24 - Carl Laemmle, Jewish media mogul and founder of Universal Pictures (b. 1867)