- Dec 1 Boys Town founded by Father Edward Flanagan west of Omaha, Nebraska
- Dec 2 Han Yong-woon, found Zen awakening at Osean Monastery Korea
- Dec 3 After nearly 20 years of planning and construction, the Quebec Bridge opens to traffic.
- Dec 3 The Supreme Allied War Council, meeting at Versailles to define war aim, fails to reach an agreement
- Dec 5 Austro-German Forces launch an offensive against the Italians on the western end of their line, around Asiago
- Dec 6 French munition ship "Mont Blanc" explodes in Halifax, kills 1,700
- Dec 6 Taking advantage of the temporary relaxation of authority in Russia, Finland declares itself a republic, following the Ukraine on 20 November
- Dec 7 US becomes 13th country to declare war on Austria during World War I
Event of Interest
Dec 7 The USA's 42nd 'Rainbow' Division arrives in France (with Colonel Douglass MacArthur among its ranks)
Douglas MacArthur
- Dec 9 British forces under General Allenby capture Jerusalem
- Dec 11 13 black soldiers hanged for participation in Houston riot
- Dec 11 German-occupied Lithuania proclaims independence from Russia
- Dec 12 French troop train derails in French Alps killing 543
- Dec 12 Rev Edward Flanagan forms Boys Town outside Omaha, Nebraska
- Dec 14 UFA, Universal Film AG, forms in Germany
- Dec 15 Moldavian Republic declares independence from Russia
- Dec 15 World War I: An armistice is reached between the new Russian Bolshevik government and the Central Powers.
Vladimir Lenin
Joseph Stalin
- Dec 18 The 18th Amendment, authorizing prohibition of alcohol, is approved by the US congress and sent to the states for ratification
- Dec 19 1st NHL game played on artificial ice in Toronto
- Dec 19 Quebec Bulldogs play their 1st professional hockey game
- Dec 20 Cheka formed - Soviet state security force and forerunner to the KGB, under Felix Dzerzhinsky after decree by Lenin
- Dec 20 A second nationwide referendum on military conscription is rejected by the Australian public
- Dec 22 Flanders declares its independence, under Pieter Tack
- Dec 23 3 British warships come close to Holland
- Dec 25 "Why Marry" 1st drama to win Pulitzer Prize, premieres in NYC
- Dec 25 Louis Hirsch and Otto Harbach's musical "Going Up" premieres in New York City
- Dec 26 1st NHL defensemen to score a goal: Toronto Maple Leaf Harry Cameron
- Dec 26 US Federal government took over operation of American railroads for duration of WW I
- Dec 30 -32°F (-36°C) in Mountain City, Tennessee (state record)
- Dec 30 -37°F (-38°C) in Lewisburg, WV (state record)
- Dec 31 Dutch Social-democratic trade union NVV counts 159,450 members