Germany's constitution, or Basic Law, was a "great gift" after the tyranny of the Nazi regime, President Frank-Walter Steimeier said at the ceremony marking the entry into force of the law 75 years ago.
"A gift that must not only be remembered, but that we must cherish, preserve and defend in the everyday life of the republic," Steinmeier said during the celebration on Thursday in Berlin.
It is one of the oldest constitutions in the world and has become a model for many constitutions, Steinmeier said.
The Basic Law was the "dawn of a brighter future," he added.
"It created a stable structure in which people could increasingly feel at home and at ease, in which society could develop and renew itself. It is the model for peaceful coexistence in a diverse society - aware of history and open to the future," Steinmeier said.
The ceremony was attended by the heads of Germany's five constitutional bodies. In addition to the president, these included the presidents of the lower and upper house of parliament, the Federal Constitutional Court as well as Chancellor Olaf Scholz.