Depending on what you feel is important, there are:
Kant (philosophy)
Bismarck (politics)
Goethe (poetry)
Beethoven (music)
Luther (religion)
Einstein (physics)
Gauss (math)
Zuse (computer science)
Koch (biology)
Daimler/Benz (engineering)
Well, I am looking forward to the (hopefully soon to come) contributions from other nations.
P.S.: Yes, I am a German.
The American, Einstein.
Now waaaiiit a second! What matters is where he was born and accomplished his greatest work, and that was Germany and Switzerland.
After emigrating to the U.S. he didn’t achieve much scientifically (his attempts to create the unified field theory never got anywhere).
Does it really matter WHERE he achieved greatness, was educated, or born?
He died as an American.
Late great ex-German, then.
Me! I am a great German … 
He died before he could finish it. The theory itself was a huge undertaking, which other notable scientists attempted unsucessfully to continue after his death. As far as I know, no progress was made for decades until the advent of computers able to perform the complex calculations. Other unified field theories do now exist although there is no definitive one.
Perhaps I read the above post wrongly, but it seems to discredit an undoubtedly great man.
It’s all relative to me