Former European Commission President Jacques Delors, described as the architect of the modern European Union, has died at the age of 98.
Delors' death news was shared by his daughter Martine Aubry.
Aubry said her father died in his sleep at his home in Paris on Wednesday morning.
The French politician was instrumental in creating the common market, which allows the free movement of people, goods and services within the Union.
Delors, in office from 1985 to 1995, also laid the foundation for the European Union's common currency, the euro.
During his presidency of the Commission, he was among those who believed that Turkey culturally and religiously did not belong in the European Union.
Delors also referred to the Union as a "Christian club" and argued that this was the reason for the difficulty in accepting Turkey.
This statement of Jacques Delors was also frequently brought up in the EU process that started after the 2002 elections when the AKP came to power.
President Erdoğan has often argued that the EU should accept Turkey as a member to prove the contrary.
'ONE OF THE FOUNDERS OF EUROPE AS WE KNOW IT'
French President Emmanuel Macron published a commemorative message praising Delors, who also served as French finance minister between 1981-84.
In this message, he referred to Delors as "the tireless architect of our Europe".
"His commitment (to the union), his ideals and his sense of fairness will always inspire us," Macron said.
Delors served three terms as president of the European Commission, making him the longest-serving president.
Ursula von der Leyen, who currently holds the post, described Delors as "a visionary who made Europe stronger".
Charles Michel, President of the European Council, referred to the French politician as "one of the founders of Europe as we know it".
Jacques Delors, a French socialist, was a firm believer in the idea of integration in the post-World War II world.
During his time at the top of the EU leadership, he pushed for the common market and the euro, as well as the Schengen visa system and the Erasmus student exchange program.
Margaret Thatcher, Britain's prime minister nicknamed the Iron Lady, and Delors were said to have hated each other.
In the late 1980s, Delors' name was at the center of controversy in the UK.
There was a bloc on the island that was skeptical of the idea of a common currency and felt that the European Parliament was trying to expand its influence.
The Sun, a British tabloid newspaper, targeted Delors, who was at the center of these initiatives, with a 1990 headline reading "Suck it, Delors".
Margaret Thatcher criticized Delors' economic policies and argued that they would take decision-making power away from the British Parliament.
It was also stated by Conservative Party figures that Thatcher and Delors mutually "hated" each other.
In 1995, Delors left his post at the EU and refused to run for the French presidency despite polls in his favor.
Delors continued to defend the ideal of the European Union and warned of the dangers of populism in Europe.