List of shortest-reigning monarchs Less than a month Less than a month

| Name_ | Country | Reign_began | Reign_ended | Length_ |
|---|---|---|---|---|
| Pope Marcellus II | Holy See | 9 April 1555 | 1 May 1555 | 22 days |
| Emperor Gordian I | Roman Empire | 22 March 238 | 12 April 238 | 21 days |
| Emperor Gordian II | Roman Empire | 22 March 238 | 12 April 238 | 21 days |
| Pope Sisinnius | Holy See | 15 January 708 AD | 4 February 708 AD | 21 days |
| Pope Theodore II | Holy See | December 897 AD | December 897 AD | 20 days |
| Emperor Shang | China | 8 July 710 | 25 July 710 | 18 days |
| King Anikanga Mahadipada | Polonnaruwa | 1209 | 1209 | 17 days |
| Pope Celestine IV | Holy See | 25 October 1241 | 10 November 1241 | 17 days |
| Pope Boniface VI | Holy See | April 896 AD | April 896 AD | 16 days |