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

| Name_ | Country | Reign_began | Reign_ended | Length_ |
|---|---|---|---|---|
| Emperor Taichang | China | 28 August 1620 | 26 September 1620 | 29 days |
| Emperor He | China | 74 BC | 74 BC | 27 days |
| Pope Leo XI | Holy See | 1 April 1605 | 27 April 1605 | 27 days |
| Pope Pius III | Holy See | 22 September 1503 | 18 October 1503 | 27 days |
| Prince Milan Obrenović II | Serbia | 25 June 1839 | 8 July 1839 | 26 days |
| Pope Damasus II | Holy See | 17 July 1048 | 9 August 1048 | 24 days |
| Emperor Constantine | Russian Empire | 1 December 1825 | 25 December 1825 | 24 days |
| Pharaoh Amenemhet VI | Egypt | c.1780 BC | c.1780 BC | 23 days |