The eagerly-awaited match is being played at St Jakob Park in Basel, Switzerland (1845 GMT) but the excitement is building in Germany which has about 2.7 million people of Turkish origin, more than in any other country in western Europe. The flags of both nations have been fluttering side by side from buildings and cars since the start of the three-week tournament being co-hosted by Austria and Switzerland.
"For us, 'we' means both Germany and Turkey so one of our teams is guaranteed a place in the final and we're very happy," Kenan Kolat, chairman of the umbrella group for Germany's Turkish communities, said on Tuesday.
"I don't expect any trouble," he told television broadcaster n-tv. "I hope people will watch the match together and then nothing can go wrong."
Organisers in Berlin, with its 170,000-strong Turkish community, said they had extended the 'Fan Mile' running through the city centre to 1.2 km (0.7 miles) and half a million people were expected to watch the match on three giant screens.
German Interior Minister Wolfgang Schaeuble urged fans from both sides to party together in a "joyful and violence-free atmosphere" and noted the lengthy soccer tradition they share.
Two members of the Turkish squad, Hamit Altintop and Hakan Balta, were born in Germany and Germany manager Joachim Loew had spells as coach of Turkish sides Fenerbahce and Adanaspor.