Not since 2004 - when Max Rauffer topped the downhill podium on the Saslong - has a German man won a downhill or super-G title but that all changed as Ferstl put down an almost flawless run.
Fog plagued the course with only 38 of 80 racers able to start their runs, but Ferstl was able to stop the clock in a time of 1:35.28.
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That was only 0.02 seconds ahead of Austria’s Max Franz, with Olympic downhill champion Matthias Mayer completing the podium line-up.
Despite a big mistake, Austrian Mayer's time was only one tenth of a second behind Ferstl's winning effort.
His victory moves Ferstl up to fourth in the super-G World Cup standings on 144 points, with Norway's Kjetil Jansrud - who placed 35th in Italy - leading the way on 180.
Austria's Vincent Kriechmayr, who finished fifth, is second in the standings with compatriot Franz in third.
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