Bolkiah, who took the throne in 1967, has reigned for 54 years and 339 days (as of Friday) -- more than four years longer than Margrethe II of Denmark, now the second-longest reigning monarch.
Sultan of Brunei Hassanal Bolkiah
The Sultan of Brunei Hassanal Bolkiah became the world's longest serving monarch with the passing of Britain's Queen's Elizabeth II, the media reported.
Bolkiah, who took the throne in 1967, has reigned for 54 years and 339 days (as of Friday) -- more than four years longer than Margrethe II of Denmark, now the second-longest reigning monarch, the Daily Mail reported.
Before her death, Her Majesty was far-and-away the longest serving monarch in the world, marking the 70th anniversary of her coronation earlier this year, the Daily Mail reported.
But while The Queen -- who came to the throne aged just 25 in 1952 in the aftermath of World War II -- has ensured that she has kept her distance from politics in the UK, the opposite can be said of Bolkiah in his home country.
In addition to being the country's Sultan and absolute monarch, 76-year-old Hassanal Bolkiah ibni Omar Ali Saifuddien III has also been the Prime Minister of Brunei since the country gained independence from the UK in 1984.
His reign has also been mired in controversy. He has faced criticism of his country's human rights record, and questions have been raised over business dealings, the Daily Mail reported.
Unlike the UK's head of state, Bolkiah enjoys absolute power in Brunei. Under the country's 1959 Constitution, the head has full executive authority - including emergency powers.
In 2006, he was reported to have amended the country's constitution to make himself infallible under the law, Daily Mail reported.
As Prime Minister, he is also the head of government - and currently holds the positions of Minister of Defence, Minister of Foreign Affairs and Minister of Finance. He also controls the country's police force.
To top it all off, he is also Head of Religion, and Islam is the official religion of the country.
In 2014, he advocated for the adoption of Islamic sharia penalties -- that includes death by stoning, the severing of limbs and flogging for some crimes. Such crimes include abortions, adultery and same-sex sexual acts, Daily Mail reported.