Leo Varadkar (38) will be the youngest serving EU leader and one of the youngest prime ministers in the world when he becomes Taoiseach in 10 days time.
Mr Varadkar was born on January 18th 1979, and he will be 38 years, five months and 26 days old when he is expected to be confirmed as Taoiseach by the Dáil on June 13th.
Ireland will then go from having the oldest serving leader in the EU - Enda Kenny (66) - to the youngest.
Until now, the Estonian prime minister Jüri Ratas has been the youngest EU leader since he assumed office in November last year.
He was born on July 2nd 1978 and is almost six months older than Mr Varadkar.
Mr Varadkar will be of three EU leaders under the age of 40. The third is the President of France Emmanuel Macron who will turn 40 in December.
The Belgian prime minister Charles Michel is the next youngest European leader. He is 41.
At the other end of the scale is German chancellor Angela Merkel (62) and the British Prime Minister Theresa May (60), assuming she is elected next week. If not Jeremy Corbyn (68) will be the oldest EU leader.
Outside the EU, the prime minister of Ukraine Volodymyr Groysman, who succeeded Arseniy Yatsenyuk in April last year, is almost exactly a year older than Mr Varadkar.
Several countries that are not democracies have leaders who are younger than Mr Varadkar.
Kim Jong-un, the leader of North Korea, who inherited his position from his father and grandfather, is 34.
The Emir of Qatar, Tamim bin Hamad Al Thani, is 36 and Jigme Khesar Namgyel Wangchuck, the King of Bhutan, is 37.
The closest in age to Mr Varadkar is Saleh Ali al-Sammad, the president of the Supreme Political Council of Yemen who is 16 days younger than him.
The youngest Taoiseach prior to Mr Varadkar is William T Cosgrave who became the president of the executive council (effectively taoiseach) at the age of 42 in 1922. His son Liam Cosgrave was 52 when he became taoiseach in 1973.
