Several hundred thousand people were expected in the northern city of Bremen for a series of street parties and official events led by Chancellor Angela Merkel, herself brought up in East Germany.
In a video podcast on the eve of the celebrations, Merkel paid tribute to East Germans for having "the courage to fight for freedom." "At the same time, there was a huge wave of solidarity from the people in West Germany. It is thanks to these joint efforts that we have been able to rebuild so quickly and make Germany a country that is respected in the World."
Also expected to attend the reunification celebrations were European Commission President Jose Manuel Barroso and NATO Secretary General Anders Fogh Rasmussen.
US President Barack Obama was quick to congratulate Germany, praising "the courage and conviction of the German people that brought down the Berlin Wall, ending decades of painful and artificial separation."
The peaceful reunification of East and West Germany was a "historic achievement," said the president. After World War II, the victorious powers, the United States, Britain, France and the Soviet Union carved defeated Germany into four sections.
With the advent of the Cold War, Moscow erected a border between its eastern section and the three western Allied sections, including the Wall that split Berlin in two.
On October 3, 1990, just under a year after the Wall was yanked down in a bloodless revolution, the reunification treaty bringing the two halves of the country together came into effect amid joyful scenes.