Monarchs whose exact dates of rule are unknown
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. The list is limited to those that might reasonably be expected to lie within the range of those in the table above.
^He was proclaimed king at the age of four months, and his grandmother, Labotsibeni Mdluli, acted as regent until 22 December 1921 and then formally transferred all monarchial power to Sobhuza II: Swaziland National Trust Commission website, retrieved 29 August 2008. TheRoyalist.net takes the date of succession as the date on which his grandmother handed over the royal duties to him, not when he was proclaimed king.
^Heinrich XI succeeded to the throne as Count of Reuss-Obergreiz in 1723 on the death of his brother, Heinrich IX (all male members of the family were named Heinrich in order of birth, even across cousins). In 1778 he became the first Prince of Reuss Elder Line.
^Count Johann Ludwig was born posthumously, after the death of his father Count Johann II on 25 July 1472; he succeeded to the throne at birth.
^Acceded to the Union of India on 15 August 1947. Merged Kapurthala into the Patiala and Eastern Punjab States Union (PEPSU) on 5 May 1948, relinquished his sovereign powers with effect from 20 August. Rajpramukh of the PEPSU from 5 May 1948 until his death on 17 June 1949
^Also a long-serving Holy Roman Emperor as Friedrich III
^More commonly known as Eleanor of Aquitaine, Aliénor was Duchess of Aquitaine in her own right, although medieval law dictated that her various husbands (Louis VII of France, Henry II of England) and sons (Richard I and John of England) reign with her jointly.
^Merged his state into the United State of Kathiawad on 15 February 1948, but lived until 28 June 1954
^This length of reign applies only to the United Kingdom, Canada, Australia, and New Zealand, as all of the other countries Elizabeth II is at present queen of had yet to gain independence at the time of her accession.
^Friedrich August I was known as Friedrich August III before 1806.
^Philipp II ruled as co-ruler with his brother till 1442 when they divided their inheritances.
^Served as Regent for his father, the Taishō Emperor, from 29 November 1921 until his formal accession.
^Longest de jure ruler of China, although the Qianlong Emperor held longer de facto power.
^Ulrich V was Count of all Württemberg until its partition between Württemberg-Urach and Württemberg-Stuttgart in 1442. He continued as Count of the latter branch until his death in 1480.
^Acceded to the Union of India on 14 August 1947, but retained sovereignty over his state until his death on 31 March 1948
^Longest de facto ruler of China, although the Kangxi Emperor held longer de jure power.
^Johann Jakob I succeeded as Truchsess (Archsteward), and was raised to the rank of Graf (Count) in 1628.
^Exceeded by Queen Victoria as monarch of United Kingdom as a part of British Empire.
^Exceeded by Queen Victoria as monarch of Scotland as part of British Empire.
^Pepi II's figure has been disputed by some Egyptologists who favour a shorter reign length of 64 years, given the absence of attested dates known for Pepi after his 31st Count, which would equate to 62 years assuming the count to be biennial. Others point however to the consistency between the existing historical sources all crediting Pepi with over 90 years of reign. Finally, the lack of evidence beyond his 62nd year does not preclude a much longer reign, especially in view of the decay of the Egyptian state into the chaos of the First Intermediate Period at the end of Pepi's reign.
^Japanese legendary emperors, according to the ancient Japanese calendar, ruled for very long terms of 60–70 years each. The longest ruler of the legendary emperors, Emperor Kōan, was claimed to have ruled for about 101 years. These figures are not included in the table because they are regarded as inaccurate by modern scholars.
^Johann Philipp succeeded to the Lordship of Stadion at age 14 in 1666, was raised to Baron in 1686 and Reichsgraf (Count) in 1704.
^Shapur II was crowned in utero: the crown was placed upon his mother's belly. This child, named Shapur, was therefore born king; the government was conducted by his mother and the magnates.
^Ernst II ruled jointly with Friedrich VIII in the years 1602–13, but then ruled for 57 years as sole monarch.