During his 16 years at the country's helm from 1982 to 1998 - first for West Germany and then all of a united Germany - Kohl combined a dogged pursuit of European unity with a keen instinct for history.
Merkel, Germany's incumbent chancellor who grew up in communist East Germany before being appointed by Kohl to her first ministerial post, said he "changed my own life path decisively" by reuniting Germany.
A left-leaning German newspaper is apologising for a front-page headline on the death of former Chancellor Helmut Kohl that some considered distasteful. "He was not only the father of German reunification, but also an advocate for Europe and the transatlantic relationship". The conversion of bankrupt East German marks for the prized western currency at an over-generous (for the East Germans) exchange rate greatly hampered the initial competitiveness of the East German economy.
European Council president Jean-Claude Juncker tweeted: "Helmut's death hurts me deeply".
He was born in the year 1930 to Catholic parents and he joined the Hitler Youth in the year 1940 just at the age of ten.
Kohl's first attempt to unseat Social Democratic Chancellor Helmut Schmidt failed in 1976, but Kohl seized his chance six years later, taking power on October 1, 1982, when a junior coalition party switched sides.
The Kremlin said Russian President Vladimir Putin had sent condolences to Germany's president and to Merkel and cited him as saying Kohl "will be remembered in Russia as a resolute supporter of friendly relations between our countries".
Juncker described Kohl as the "very essence of Europe". He celebrated the European Union's eastward expansion in 2004 with a speech declaring that "the most important rule of the new Europe is: There must never again be violence in Europe". His oldest brother, Walter, was killed in action a few months earlier.
On Saturday, the daily Tageszeitung's headline was "Blooming Landscapes", an allusion to Kohl's promise of an economically flourishing eastern Germany, over a picture of wreaths.