Longest-Serving Living Monarchs
HM Queen Elizabeth II continues her reign at the top
Though less common now than they once were, monarchs have had an important role in history since at least the 3000s B.C.E. These are the living rulers who have been part of more history than the rest.
Qaboos bin Said
Carl XVI Gustaf
Who Qualifies for the Running
For the purposes of our list, we've only considered the monarchical heads of state1 of entire countries2. This means that we have left off Sheikhs Sultan bin Muhammad Al-Qassimi III, Hamad bin Mohammed Al Sharqi, and Humaid bin Rashid Al Nuaimi. These three rule emirates of the United Arab Emirates. If included, they would have been in the top six. However, the nominal leader of the UAE is Khalifa bin Zayed bin Sultan Al Nahyan, the emir of Abu Dhabi.
We have also left off Ahmad Shah, Sultan of Pahang, as Pahang is a province of Malaysia.
As of 2018, there is only one ruler on the list who has declared their intention of abdicating their position. Emperor Akihito will be stepping down from the Chrysanthemum Throne in April, 2019, at which point King Abdullah II of Jordan will most likely make the list.
Queen Elizabeth II, if we tracked all of her different accession dates, would occupy 1st, 2nd, 3rd, 7th, 9th, and 10th place. We've tracked from the date she became queen of the United Kingdom, Australia, Canada, and New Zealand. However, Her Majesty is the ruler of 16 countries, of which she assumed rulership at different times.
In addition, Queen Elizabeth is the only monarch on the list to rank among the longest-reigning monarchs of all time. Per the conditions we've used above, she would rank 9th all-time. If she continues to reign for two more years, she will surpass Emperor Constantine VIII of the Eastern Roman Empire and Emperor Franz Joseph I of Austria-Hungary to reach 7th place. She would have to reign for 16 more years to take first place from King Sobhuza II of Swaziland.
1. A country's head of state is it's public representative, a figure who's meant to stand for the nation and speak for its people. In a presidential system, like in the United States, the president is both the head of state and the head of government (the person who holds executive power). This is also true in an absolute monarchy. In a constitutional monarchy, however, the monarch is only head of state. We are considering monarchs constitutional and otherwise.
2. The benchmark we're using to delineate an "entire country" is whether or not the government represented by a monarch is legally subordinate to another government. The Sultan of Pahang, for example, is the legitimate ruler of Pahang. However, the government of Pahang is beneath the government of Malaysia. By contrast, the government of the U.K. does not have any direct superior body.