The eldest son of the last ruler of the Austro-Hungarian empire has died in Germany at the age of 98.
Otto von Habsburg was born in 1912, as the heir to the empire, but it collapsed at the end of World War I and the Habsburg family went into exile.
After World War II, Mr Habsburg became a champion of European unity during its Cold War division.
He served as a member of the European parliament for two decades. He is to be buried in the Austrian capital, Vienna.
Mr Habsburg only officially relinquished his claim to inherit the empire in 1961 and five years later was allowed to return to Austria for the first time since the family fled in 1919.
He was an opponent of the Nazis and spoke out against Germany's annexation of Austria in 1938.
In 1989 he helped organise the Pan-European Picnic demonstration on the border of Austria and Hungary.
The border was briefly opened, an event credited with helping usher in the fall of the Berlin Wall months later.
Mr Habsburg then dedicated himself to having the former communist-ruled states of eastern Europe brought into the EU.
European Commission President Jose Manuel Barroso paid tribute to him as "a great European... who gave an important impetus to the European project throughout his rich life".