Genetic material was taken in 2006 from the skull, kept in a tomb in Weimar, central Germany, where Schiller and fellow author Johann Wolfgang Goethe lived, and compared to material from the graves of Schiller relatives.
Schiller (1759-1805), who wrote influential plays critical of inequality, has no direct descendants still alive.
The skull was recovered from a royal courtiers' mass grave in Weimar 21 years after his death as a cult developed around him, and it was treated for 180 years as Schiller's, based on many points of resemblance to his appearance.
"The DNA analysis shows without a shadow of a doubt that this is not the author's skull," Julia Glesner, a spokeswoman for the Weimar Foundation which preserves the German Classicist heritage, said on Saturday, May 3.
Adding to the mystery is a controversy over a second skull found in 1911 in the same mass grave, regarded by some as Schiller's. But the DNA tests found it too belonged to someone else.
The Weimar Foundation sponsored the study in cooperation with the MDR public broadcasting corporation, triggering controversy over whether dead bodies should be exhumed for the sake of curiosity.
One Catholic priest, Wilfried Braun, refused permission for a relative to be exhumed, saying he could not perceive any useful purpose in the venture that justified disturbing the dead.
Now the foundation must resolve what to do with the bones of the "wrong" Schiller, whose identity remains unknown.