|Year:||1817 1818 1819 – 1820 – 1821 1822 1823|
1820 (MDCCCXX) was a leap year starting on Saturday of the Gregorian calendar
- January 29 – George IV of the United Kingdom ascends the throne, ending the period known as the British Regency. There will be a gap of 21 years before the title Prince of Wales is next used.
- March 15 – Maine is admitted as the 23rd U.S. state.
- May 11 – The HMS Beagle (the ship that later takes young Charles Darwin on his scientific voyage) is launched.
- December 3 – U.S. presidential election, 1820: James Monroe is re-elected, virtually unopposed.