Today, Queen Elizabeth II of the United Kingdom surpasses King Rama IX of Thailand to become the second longest-reigning monarch. King Rama IX, also known as Bhumibol Adulyadej, reigned from 9 June 1946 until his death on 13 October 2016. He was 88 years old at the time of his death.
Only last month, Queen Elizabeth surpassed Johann II, Prince of Liechtenstein, to become the third longest-reigning monarch in history. Johann II ruled the principality of Liechtenstein between 1858 and 1929. He succeeded his father on 12 November 1858 upon his death at the age of 62. Johann had just turned 18 the month before. He reigned until his own death at the age of 88 on 11 February 1929. He never married and was succeeded by his brother Franz I.
Queen Elizabeth became the fourth longest-reigning monarch in March 2020 and surpassed Eleanor of Aquitaine, who ruled the Duchy of Aquitaine in her own right, as the longest-reigning female ruler in 2019. In 2015, she surpassed her great-great-grandmother Queen Victoria to become the longest-reigning British monarch.
However, the longest-reigning monarch in history remains King Louis XIV of France, and he reigned for 26,407 days. Queen Elizabeth will reach that milestone on 24 May 2024, by which time she’ll be 98 years old.