Wikipedia:Selected anniversaries/October 20
- 1740 - Maria Theresa, an "enlightened monarch", assumed the throne of Austria, succeeding her father, Charles VI.
- 1827 - An allied British, French, and Russian naval force destroyed a combined Turkish and Egyptian fleet at the Battle of Navarino, a decisive moment in the Greek War of Independence.
- 1935 - The Chinese People's Liberation Army completed the Long March from Jiangxi province in southern China to in Shaanxi province, an organized maneuver covering a distance of 6000 km (3700 mi).
- 1968 - Former U.S. First Lady Jacqueline Kennedy (pictured right) married Greek shipping business magnate Aristotle Onassis.
- 1973 - The Sydney Opera House was formally opened by Queen Elizabeth II. The opening was televised and included fireworks and a performance of Beethoven's Symphony No. 9.
Recent days: October 19 - October 18 - October 17