1820 was a leap year starting on Saturday
- January 3 - publishing of the "Yerkragund"
- August 8 - demonstration of Armenian commoners in Constantinople
- September 18 - Grigor Sakayan, Hakob Kesaratsi, and Deli Baghdasar are condemned to death for demonstrating against the sultan.
- February 19 - Hovsep Gatrchyan, historian (d.1882)
- April 4 - Catholicos Mkrtich Khrimyan "Hairik" (d.1907)
- July 6 - Ghevond Alishan, armenologist (d.1901)
- September 18 - Chamik Aramyan, publisher (d.1878)