The 87-year-old led Germany from 1982 to 1998
Former German Chancellor Helmut Kohl has died aged 87.
He led Germany from 1982 to 1998 during the reunification of east and west.
German Foreign Minister Sigmar Gabriel says he was "a great German statesman and above all a great European".
In a statement, President Michael D Higgins said: "It is with sadness that I have learned of the death of former Chancellor of Germany, Helmut Kohl.
"He will be remembered for his 16-year tenure as Chancellor, as well as for his role in the reunification of East and West Germany in 1990.
"His deep commitment to the European project was unshakable, referring as he often did to the common European House, in the construction of which everyone would have a role.
"On behalf of the people of Ireland I wish to convey my deepest sympathies to his family and to the people of Germany."
Former US President Bill Clinton said: "I am deeply saddened by the passing of my dear friend, Helmut Kohl, whose visionary leadership prepared Germany and all of Europe for the 21st century.
"He was called upon to answer some of the most monumental questions of his time, and in answering them correctly he made possible the reunification of a strong, prosperous Germany and the creation of the European Union.
"I will never forget walking with him through the Brandenburg Gate in 1994 for a large rally on the eastern side, and seeing genuine hope in the eyes of tens of thousands of young people.
"I knew at that moment that Helmut Kohl was the man who could help them realize their dreams. History continues to prove that he delivered.
"As the world remembers a leader who was strong in more than stature, Hillary and I send our thoughts and prayers to Maike, Helmut's sons, Walter and Peter, and the people of Germany."
NATO Secretary-General Jens Stoltenberg said Kohl was "the embodiment of a united Germany in a united Europe.
"When the Berlin Wall fell, he rose to the occasion. A true European."
Helmut Kohl was the embodiment of a united Germany in a united Europe. When the Berlin Wall fell, he rose to the occasion. A true European.— Jens Stoltenberg (@jensstoltenberg) June 16, 2017
President of the European Council Donald Tusk said he will remember Kohl as "a friend and a statesman who helped reunite Europe."
I will always remember Helmut Kohl. A friend and a statesman who helped reunite Europe.— Donald Tusk (@eucopresident) June 16, 2017
Mr Kohl visited Ireland for two days back in 1996.