Mr Renzi speared the referendum as he wanted to streamline the current political system in the country to push through with his economic reforms after years of a bad economy.
But over the course of Sunday evening, it became resolutely clear the that the ‘No’ campaign was leading with almost 60 per cent of the vote.
Mr Renzi had promised to resign if the country did not vote in line with his plans for reform. He will hand his resignation to the Italian President Sergio Mattarella on Monday, Mr Matterella will then appoint a new government or if unable to do that will call for an early election.
The financial markets reacted immediately to the result with the euro falling sharply against the dollar. There are concerns that the "No" result will boost the prospects of opposition groups who wish to take Italy out of the eurozone.
So who is the man who spearheaded the referendum?
Born in 1975 in Florence as one of four children, he grew up in a Catholic family in the Italian city.
With a clear passion for politics from a young age, he was a teenage campaign volunteer for the previous Prime Minister and chief of the European Commission Romano Prodi.
He graduated with a degree in law from University of Florence then went straight into politics, albeit for a stint working for his family’s advertising business in his twenties, He then became the leader of a province in Florence at just 29-years-old.
By 34, he was the Mayor of Florence and later, after what has been described as an ‘internal coup’, he became leader of the Democratic Party. In 2014, he became Italy’s fourth Prime Minister in less than three years at the age of 39, establishing himself in the history books as being Italy’s youngest ever premier. His rise to power in the party has been criticised by some, especially after an infamous tweet where he reassured the then-PM Enrico Letta: “Enrico, keep calm, no one wants to take your job”.
Time as Prime Minister
Viewed as a fresh, young politician arriving to shake things up, his tendency to dress casual in open neck shirts and jeans helped to fuel that appeal. When he was not casual, he favoured high-end Italian brands such as Georgio Armani.
He is also active on Twitter and has a reputation for speaking his mind, so much so that Vogue notes he has been dubbed the “bad boy of Europe”. He has criticised the EU's response to the migration crisis and called for Eastern European countries not accepting refugees to have their EU funding culled.
During his first 1000 days in office, he is credited with helping to recover the economy and securing a controversial Jobs act. However, there have been accusations over how effective this bill was.
Renzi also helped to pass a long-awaited bill on same-sex civil partnerships yet in order to pass it due to opposition from Catholic conservatives he toned it down by dropping a clause on adoption rights for gay people.
Renzi is married to humanities schoolteacher Agnese Landini - who is his teenage sweetheart. The couple have three children: Francesco, Emanuele and Ester.
Vogue commented that Mr Renzi “exudes confidence and almost mischievous nonchalance” – something that has perhaps changed since the outcome of his referendum – and is “disarmingly charming”.
Mr Renzi joined the era of the ‘cool’, relatable young world leaders like Barack Obama and Justin Trudeau, with Mr Renzi and the Canadian Prime Minister taking a selfie together in March and Mr and Mrs Renzi joining the Obamas for their final ever state dinner in October. However, the Associated Press suggests he never quite reached that level of cool as an ex-Catholic boy scout.
Mr Obama even contributed to Mr Renzi’s Vogue interview praising his “progressive, forward-looking vision for the future of his country” and said he was impressed with “his passion for European solidarity”.
Tony Blair was another contributor calling him “one of the most important things to happen in Europe in several years.”
During his concession, Mr Renzi said his "experience of government finishes here” and wished his country good luck in their future. As Mr Renzi has had a wealth of political experience despite his young age, it remains to be seen whether he will totally leave the political world.
Ahead of the referendum, he signalled his options for his next career move remain open. “I’ll go home and do something else with my life,” he told Vogue”. “I’m 41. I can do anything, with a smile”.
Additional reporting by the Associated Press.
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