1925
Events
January
- January 1 - The Syrian Federation is officially dissolved, the State of Aleppo and the State of Damascus having been replaced by the State of Syria.
- January 3 - Benito Mussolini makes a pivotal speech in the Italian Chamber of Deputies which will be regarded by historians as the beginning of his dictatorship.
- January 5 - Nellie Tayloe Ross becomes the first female governor in the United States. Fifteen days later, Miriam A. Ferguson becomes first female governor of Texas.
- January 25 - Hjalmar Branting resigns as Prime Minister of Sweden because of ill health, and is replaced by the minister of trade, Rickard Sandler.
- January 27–February 1 - The 1925 serum run to Nome relays diphtheria antitoxin by dog sled across the U.S. Territory of Alaska to combat an epidemic.
February
- February 25 - Art Gillham records the first Western Electric masters to be commercially released.
- February 28 - The 1925 Charlevoix–Kamouraska earthquake strikes northeastern North America.
March
- March 1 - New York City Fire Department Rescue 2 is put in service in Brooklyn.
- March 4
- * İsmet İnönü is appointed prime minister in Turkey.
- March 6 - Pionerskaya Pravda, one of the oldest children's newspapers in Europe, is founded in the Soviet Union.
- March 9–May 1 - Pink's War: The British Royal Air Force bombards mountain strongholds of Mahsud tribesmen in South Waziristan.
- March 15 - The Phi Lambda Chi fraternity is founded on the campus of Arkansas State Teachers' College in Conway, Arkansas.
- March 16 – At 22:42 local time a 7.0 earthquake shakes the Chinese province of Yunnan killing 5,000 people.
- March 18 - The Tri-State Tornado, the deadliest in U.S. history, rampages through Missouri, Illinois and Indiana, killing 695 people and injuring 2,027. It hits the towns of Murphysboro, Illinois; West Frankfort, Illinois; Gorham, Illinois; Ellington, Missouri; and Griffin, Indiana.
- March 21 - Ravel's opera L'enfant et les sortilèges, to a libretto by Colette, is premiered at the Opéra de Monte-Carlo.
- March 31 - The Bauhaus closes in Weimar and moves to a building in Dessau designed by Walter Gropius.
April
- April–October - The Exposition Internationale des Arts Décoratifs et Industriels Modernes is held in Paris, giving a name to the Art Deco style.
- April 1 - In the United States:
- * Frank Heath and his horse Gypsy Queen leave Washington, D.C. to begin a two-year journey to visit all 48 states.
- * The Patent and Trademark Office is transferred to the Department of Commerce.
- April 10 - F. Scott Fitzgerald's novel The Great Gatsby is published in New York.
- April 15 - Fritz Haarmann, a serial killer convicted of the murder of 24 boys and young men, is guillotined in Germany.
- April 16 - A communist assault on St Nedelya Church claims roughly 150 lives in Sofia, Bulgaria.
- April 19 - Colo-colo, a well-known football club of Chile, is founded in Macul, suburb of Santiago.
- April 20 - Iranian forces of Reza Shah occupy Ahvaz and arrest Sheikh Khazʽal Ibn Jabir.
- April 28 - Presenting the Stanley Baldwin government's budget, Chancellor of the Exchequer Winston Churchill announces Britain's return to the gold standard.
May
- May 1
- * In the Destruction of early Islamic heritage sites in Saudi Arabia, the al-Baqi' mausoleums are destroyed by King Ibn Saud.
- * Barcelona S.C. founded in Ecuador.
- * The All-China Federation of Trade Unions, the world's largest trade union organisation, is founded in Guangzhou, Republic of China.
- May 5 - The General Election Law is passed in Japan, extending suffrage to all males aged 25 and over.
- May 8 - African-American Tom Lee rescues 32 people from the sinking steamboat M.E. Norman on the Mississippi River.
- May 16 – The first modern performance of Claudio Monteverdi's opera Il ritorno d'Ulisse in patria takes place in Paris.
- May 21 - The opera Doktor Faust, unfinished when composer Ferruccio Busoni died, is premiered in Dresden.
- May 29 - English explorer Percy Fawcett sends a last telegram to his wife before he disappears in the Amazon.
June
- June 6 - The Chrysler Corporation is founded as an automobile manufacturer by Walter Chrysler in the United States.
- June 13 - American engineer Charles Francis Jenkins achieves the first synchronized transmission of pictures and sound, using 48 lines and a mechanical system in "the first public demonstration of radiovision".
- June 14
- * The Aristotle University of Thessaloniki in Greece is founded.
- * The Turkish football club Göztepe is founded.
- June 29 - The 6.8 Santa Barbara earthquake affects the central coast of California with a maximum Mercalli intensity of IX, destroying much of downtown Santa Barbara, California and leaving 13 people dead.
July
- July 10–21 - Scopes trial: in a staged test case in Dayton, Tennessee, United States, John T. Scopes, a young high school science teacher is accused of assigning a reading from a state-mandated textbook on Darwinian evolution in violation of a Tennessee state law, the "Butler Act". He is found guilty and fined $100, though the verdict is later overturned on a technicality. The trial makes explicit the fundamentalist–modernist controversy within the Presbyterian Church in the United States of America, with William Jennings Bryan being challenged by the liberal Clarence Darrow.
- July 10 - Meher Baba begins his 44-year silence.
- July 18 - Adolf Hitler publishes Volume 1 of his personal manifesto Mein Kampf in Germany.
- July 21 - English racing motorist Malcolm Campbell becomes the first man to exceed on land when at Pendine Sands in Wales he drives a Sunbeam 350HP automobile at a two-way average speed of.
- July 25
- * The Telegraph Agency of the Soviet Union is established.
- * The Temporary Slavery Commission of the League of Nations filed their report on their global investigation of slavery and slave trade, preparing the ground for the introduction of the 1926 Slavery Convention.
- July 29 - Werner Heisenberg, Max Born and Pascual Jordan published Umdeutung paper in Zeitschrift für Physik in Germany
August
- August 1 - The New Cape Central Railway between Worcester and Voorbaai is incorporated into the South African Railways.
- August 8 - The Ku Klux Klan, the largest fraternal racist organization in the United States, demonstrates its popularity by holding a parade with an estimated 30,000-35,000 marchers in Washington, D.C.
- August 14 - The original Hetch Hetchy Moccasin Powerhouse in California is completed and goes on line.
- August 25 - The French complete their evacuation of the Ruhr region of Germany.
- August 31 - Anthropologist Margaret Mead lands in American Samoa to begin nine months of field work that will culminate in her 1928 book Coming of Age in Samoa. The bestselling book will become the first popular anthropological study and will change many attitudes towards tribal peoples.
September
- September 3 - The U.S. Navy dirigible Shenandoah breaks up in a squall line near Caldwell, Ohio, killing 14 crewmen.
- September 27 - Feast of the Cross according to the Old Calendar: a celestial cross appears over Athens, Greece, while the Greek police pursues a group of Greek Old Calendarists. The phenomenon lasts for half an hour.
- October - The major money forgery and fraud of Alves dos Reis is exposed in Portugal.
- October 1 - The US Congress grants permission for Gutzon Borglum to begin constructing Mount Rushmore National Memorial on federal land in South Dakota.
- October 2 - In London, UK, John Logie Baird successfully transmits the first television pictures with a greyscale image.
- October 4 - S2, a Finnish Sokol class torpedo boat, is sunk during a fierce storm near the coast of Pori in the Gulf of Bothnia, taking with her the whole crew of 53.
- October 5–16 - The Locarno Treaties are negotiated.
- October 19–29 - A brief conflict occurs between Bulgaria and Greece after a Greek soldier accidentally crosses into the Bulgarian side and was shot by border guards.
November
- November 9 - Formal foundation date of the Schutzstaffel as a personal bodyguard for Adolf Hitler in Germany.
- November 14
- * 1925 Australian federal election: Stanley Bruce's Nationalist/Country Coalition Government is re-elected with an increased majority, defeating the Labor Party led by Matthew Charlton.
- * The first Surrealist art exhibition opens in Paris.
- November 17 - The New Zealand and South Seas International Exhibition, a world's fair, opens in Dunedin, New Zealand.
- November 24 - The silent film El Húsar de la Muerte is released in Santiago, Chile.
- November 26 - Prajadhipok is crowned as King of Siam.
- November 28 - The weekly country music-variety radio programme Grand Ole Opry is first broadcast on WSM radio in Nashville, Tennessee, as the "WSM Barn Dance".
December
- December 1 - The Locarno Treaties are signed in London, intended to secure the post-war continental European territorial settlement.
- December 11 - Pope Pius XI's encyclical Quas primas, on the Feast of Christ the King, is promulgated.
- December 12 - The first motel in the world, the Milestone Mo-Tel, opens in San Luis Obispo, California.
- December 14 - Wozzeck, Alban Berg's first opera, is premiered at the Berlin State Opera conducted by Erich Kleiber.
- December 15 - Reza Shah takes the oath to become the first shah of Persia of the Pahlavi dynasty.
- December 25 - IG Farben is formed by the merger of six chemical companies in Germany.