Former West German Chancellor Helmut Schmidt, who led the country for eight years at the height of the Cold War, died on Tuesday at the age of 96, his office said.
Schmidt was West Germany's second centre-left Social Democrat (SPD) chancellor from 1974 to 1982 and a leading proponent of European integration.
He became chancellor at a time of crisis for West Germany, replacing Willy Brandt, who had been forced to resign when his close assistant Guenter Guillaume was uncovered as a Stasi agency spying for the East German intelligence agency.
At the same time, Schmidt had to deal with the consequences of the 1973-74 oil crisis.
German media reported that Schmidt caught an infection after having surgery to remove a blood clot from his leg about two months ago. He died on Tuesday in his hometown of Hamburg.
In recent years, Schmidt, a chain smoker, was a frequent talk show guest and won more respect among many Germans as an elder statesman than he did when he led the country.
"We are mourning Schmidt and are proud that he was one of us. We will miss his powerful judgement and advice," tweeted SPD leader and Vice Chancellor Sigmar Gabriel.
Conservative Chancellor Angela Merkel was to make a statement later in the evening.
His death prompted tributes from across Europe.
"A great German statesman has gone," French President Francois Hollande said. "He led his country at a very difficult time and he led it towards economic stability and towards the choice of growth."
Hollande added that Europe owed the existence of the euro to Schmidt.
As chancellor, Schmidt tried to balance a conciliatory tone towards Moscow and Communist East Germany with a strengthening of West Germany's standing within NATO and Europe.
Schmidt, who had served as finance minister from 1972 to 1974, was in office at the time of West Germany's 'economic miracle' although, recognising a worsening situation, he tried to make some welfare cuts.
One of his biggest challenges was dealing with the ultra-left Red Army Faction (RAF), whose attacks on the political and business establishment included a wave of killings and kidnappings that peaked in the 'German Autumn' of 1977.
Schmidt was succeeded by conservative chancellor Helmut Kohl.
European Commission President Jean-Claude Juncker said he had lost a friend with political courage.
"The history of this continent shaped him for almost a century and made him a committed European," said Juncker.
He said that he, together with former French President Giscard d'Estaing, had founded a European currency system and so paved the way for the euro.
Born in the northern port of Hamburg in 1918, Schmidt fought in World War Two and was taken prisoner by the British.
He was married for 68 years to Loki, his childhood sweetheart. She died in 2010. They had a son who died in his first year and later a daughter.