German Foreign Minister Sigmar Gabriel says former German Chancellor Helmut Kohl was "a great statesman, a great German politician and most of all, a great European".
UN Secretary General Antonio Guterres also mourned Kohl as a "personal friend" and praised his historical role in uniting Germany, according to his spokesman Stephane Dujarric.
As the Cold War ended with the Berlin Wall coming down in November 1989, he moved to "grab the mantle of history", as he later said, forging a political stature commensurate with his towering height.
"Future historians will say Europe's 21st century began on his watch", former US President Bill Clinton said in 1999 when awarding Kohl the Presidential Medal of Freedom.
FILE - The June 10, 1984 file photo shows Britain's Queen Elizabeth II, second left, standing with, West German Chancellor Helmut Kohl, left, U.S. President Ronald Reagan, second right, and Britain's Prime Minister Margaret Thatcher at London's Buckingham Palace, prior to a dinner for summit leaders. At the same time, he was involved in the recently formed Christian Democratic Union party, serving in a series of regional positions in the late 1950s and throughout the 1960s.
Former US President George H.W. Bush, who cooperated with Kohl and the Soviet leader Mikhail Gorbachev to reunite East and West Germany at the end of the Cold War, also mourned Kohl's death. "My mentor, my friend, the very essence of Europe, he will be greatly, greatly missed", the former Luxembourg premier said on Twitter.
He ascended to the top of West German national politics in 1973 when he became CDU chairman, and he fought the 1976 elections as his party's candidate for chancellor of Germany.
Kohl was the chancellor of then West Germany between 1982 and 1990 and the reunified Germany between 1990 and 1998.
French President Emmanuel Macron called Kohl an architect of French-German friendship.
In a poignant gesture of reconciliation in 1984, Kohl held hands with Mitterrand during a ceremony at a World War I cemetery in Verdun, France.
He won voters in bleak communist East Germany by promising them "flourishing landscapes".
Until his death, Kohl refused to identify the donors, saying he had given them his word.
Kohl leaves behind his wife and two children from a previous marriage.
Mattarella went on: "He who was, rightly, described as "the Chancellor of Reunification", worked with far-sightedness and determination, in years marked by deep and epochal changes in world equilibria, to give back unity to his country in the framework of the great project of European integration".