Records of heads of state

• 
  Sobhuza II the longest-ruling verifiable monarch ever known.
• 
  Louis XIV, the longest-ruling verifiable sovereign monarch.
• 
  Elizabeth II, the longest-ruling current monarch.

The longest undisputed reigning monarch is Sobhuza II, who ruled the Kingdom of Swaziland under the title of Paramount Chief of Swaziland and later King of Swaziland. He ruled for 82 years. However, the longest undisputed reigning ruler of a sovereign state is Louis XIV, who ruled Kingdom of France for 72 years.

Longest-ruling monarch, whose exact dates of rule are unknown is disputed between the following candidates

• Minhti, who ruled the Kingdom of Arakan as an absolute monarch under the title of King of Arakan. He is believed to have ruled for 95 years; however, little documentary evidence exists for this claim.

• Pepi II Neferkare, who ruled the Kingdom of Egypt as an absolute monarch under the title of Pharaoh of Egypt. He is believed to have ruled for either 94 or 64 years.

• Taejo of Goguryeo, who ruled Goguryeo as an absolute monarch under the title of Taewang ("The Greatest of all Kings"). He is believed to have ruled for either 93 years or 68 years.

Japanese legendary emperors, according to the ancient Japanese calendar, reigned for very long terms of 60–70 years each. The longest ruler of the legendary emperors, Emperor Kōan, was claimed to have reigned for about 101 years. These figures are not included in the list because they are regarded as inaccurate by modern scholars.

The longest current reigning male monarch is Hassanal Bolkiah, who is the Sultan and Yang di-Pertuan of Brunei ("(he) who is Lord"), an absolute monarch of Brunei Darussalam (which was a British protectorate until independence at the end of 1983).

The longest current reigning constitutional male monarch is Carl XVI Gustaf, who is the King of Sweden, a sovereign state throughout his reign.

The longest reigning female monarch ever is Elizabeth II, who is currently the Queen of the United Kingdom and other Commonwealth realms, and is a constitutional monarch. She has been Queen of the United Kingdom, Australia, Canada, and New Zealand, since 6 February 1952, (the other countries she is at present queen of were not independent at the time of her accession). The previous record was held by Eleanor of Aquitaine (who ruled for 66 years, although the sovereignty of her realms is debatable) until she was surpassed by Elizabeth in 2019.

• 
  Fidel Castro, longest-serving non-royal head of state.
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  Teodoro Obiang Nguema Mbasogo, the longest-serving president ever.
• 
  Vigdis Finnbogadottir, the longest serving female non-royal head of state.

The longest-serving non-royal head of state in the 20th and 21st centuries was Fidel Castro, who held the titles of Prime Minister of Cuba, First Secretary of the Integrated Revolutionary Organizations, First Secretary of the Central Committee of the United Party for the Socialist Revolution of Cuba, First Secretary of the Central Committee of the Communist Party of Cuba, President of the Council of State, and President of the Council of Ministers of the Republic of Cuba. He served overall for 52 years, 2 months, and 3 days but was only head of state from 1976 to 2008 (31 years, 2 months and 22 days).

The longest-serving and longest current serving male president ever is Teodoro Obiang Nguema Mbasogo, who is currently the President of the Republic of Equatorial Guinea, who seized power in a coup in 1979.

The longest serving female non-royal head of state and longest serving female president ever was Vigdís Finnbogadóttir, who was the President of the Republic of Iceland. She served for 16 years.

The oldest ruler, whose date of birth is known, is Giovanni Paolo Lascaris. He was Grand Master of the Order of Saint John until his death at the age of 97 years 47 days. The oldest ruler at the time of taking office is Prem Tinsulanonda, who became regent of Thailand at 96 years 97 days old and ruled for several months.

According to legends, the youngest ruler is Shapur II who was crowned in utero when a crown was placed on the belly of Hormizd II's wife after Hormizd II died. However, according to Shapur Shahbazi, it is unlikely. Other claims as the youngest ruler include John I of France and Alfonso XIII of Spain who were both crowned on the day of their birth. Youngest non royal ruler is Jean-Claude Duvalier who became President of Haiti at the age of 19.

The longest lived undisputed head of state is the President of Turkey Celâl Bayar who lived from 1883 to 1986, and died at 103 years old and 98 days. The Oldest undisputed Monarch is Abdul Momi who was Sultan of Brunei and lived for 97 years, 8 days.

The shortest lived known head of state is Jean I of France who ruled and lived for five days in 1316.

Officially, the current Emperor of Japan, Naruhito is the 126th in line from the first emperor, Jimmu, who is variously believed to have reigned in the 1st or 7th century BC. The earliest documentary evidence is only for the 29th emperor, Kinmei (AD 509–571); however, this is sufficient such that even the most conservative of estimates still places the Japanese imperial family as among the oldest lines in the world today.

Queen Elizabeth II of the United Kingdom is well-documented as being descended from Arnulf of Metz (c. AD 582–640), forefather of Charlemagne, thus representing a lineage of 47 generations. (See Descent of Elizabeth II from the Franks.)

The Ottoman Empire lasted for 36 sultans in 21 generations, from Osman I to Mehmed VI for 623 years. (See List of sultans of the Ottoman Empire.)

The heaviest monarch is believed to have been Taufa'ahau Tupou IV, King of Tonga from 1965 to 2006 who at his peak in 1976 was measured as 208.7 kg (460 lb), though he subsequently lost around 40% of his weight.[2]

President Benito Juárez of Mexico was reportedly the shortest world leader, standing at 4 ft 6 in (1.37 m).