List of longest-reigning monarchs

This is the list of the longest-reigning monarchs of all time, detailing monarchs and lifelong leaders who reigned for more than 50 years, sorted by length of reign.
 * Currently reigning monarchs are highlighted.
 * Note: the abbreviation (HRE) indicates a sovereign state within the Holy Roman Empire.

Monarchs whose exact dates of rule are unknown

 * Note: These monarchs are grouped according to length of reign by year in whole numbers. Within each year-grouping, they appear in historical order. In a given year, there may have been a wide array of actual reign lengths based on days. Thus, this table does not present a pure ranking of monarchs.