- Jan 2 Elara, a satellite of Jupiter, discovered by Charles Dillon Perrine in San Jose, California
- Jan 2 In Chicago, Illinois, a conference of 23 industrial trade unionists issues the 'Industrial Union Manifesto' calling for a convention to be held in Chicago in June, laying the groundwork for the formation of Industrial Workers of the World (IWW)
- Jan 2 Japanese troops capture Port Arthur from Russia, a blow to national morale and causing further discontent within Russia
- Jan 5 Charles Perrine announces discovery of Jupiter's 7th satellite, Elara
- Jan 5 Incorporation of the National Association of Audubon Society, a nonprofit environmental organization dedicated to conservation
- Jan 14 Raymond Hubbell, Sam Shubert & Robert Smith's musical "Fontana" opens at the Lyric Theatre, NYC; runs 298 for performances
- Jan 16 Baseball outfielder Frank Huelsman completes eighth transaction in 8 months
- Jan 16 Stanley Cup, Dey's Arena, Ottawa, Ontario: Ottawa Senators rout Dawson City (Yukon), 23-2 for 2-0 series sweep; most lopsided challenge playoff game in history; Frank McGee 14 goals
- Jan 17 Punchboards patented by Charles Brewer & C G Scannell, Chicago
- Jan 18 French government of Combes falls
US Supervises Dominican Debt
Jan 20 US begins supervising the Dominican Republic's national and international debts, testing President Theodore Roosevelt's "Corollary" to the Monroe Doctrine
- Jan 22 Dutchman Coen de Koning wins the 1,500m, 5,000m & 10,000m at World Allround Speed Skating Championships in Groningen, Netherlands to become 2nd Dutchman to win a world title
1905 Russian Revolution
Jan 22 In St Petersburg, Russia, a large demonstration of workers led by Father Gapon, march to the Winter Palace with a petition to the Tsar; troops fire on protesters in what becomes known as 'Bloody Sunday'
Pelleas und Melissande
Jan 25 Arnold Schoenberg's symphonic poem "Pelleas und Melissande" premieres at the Musikverein in Vienna, Austria
- Jan 26 Han Yong-woon [Bongwan, Manhae] (1879-1944) ordained a monk in Korea
World's Largest Diamond Discovered
Jan 26 World's largest diamond, the 3,106-carat Cullinan, is found in South Africa
- Jan 27 Maurice Rouvier forms government in France
Nicolas II's Worker Reforms
Jan 29 Tsar Nicolas II of Russia, unsettled by the rising violence and protest, enacts reforms to improve the conditions of workers; these changes will do little to stop disorder throughout Russia in ensuing months
- Jan 31 1st automobile to exceed 100 mph (161 kph), British daredevil Arthur Macdonald drive a Napier six-cylinder racing car named 'Samson' on sands of Daytona Beach, Florida, notching a top speed of 104 mph
- Jan 31 Carroll Wright appointed 1st Commissioner of Labor, USA
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