Austria's Diethart wins Four Hills
Austria's Thomas Diethart competes during the Four Hills competition of the FIS Ski Jumping World Cup in Bischofshofen on January 6, 2014
Diethart, 21, a virtual unknown just three weeks ago, beat his compatriot Thomas Morgenstern and Swiss four-time Olympic champion Simon Ammann to take the tournament trophy.
He scored 296.5 points after two jumps, beating Slovenia's Peter Prevc with 294.8 points and 2011 Four Hills winner Morgenstern with 293.6 points.
This gave him a total 1012.6 points over four events and makes it six wins in a row for the Austrian team at the prestigious tournament, which began on December 29 in Oberstdorf, Germany.
Diethart was already leading the Four Hills standings going into Monday's event.
The youngster with the distinctive earrings shot to the top of the standings on New Year's Day in only his sixth World Cup outing.
Still ahead after Saturday's event in Innsbruck, which was cut short due to strong winds, he gave a commanding performance in Bischofshofen on Monday, surpassing his closest rival Ammann in a first-round duel.
Ammann, affectionately nicknamed Harry Potter since he won his first Olympic gold medals in Salt Lake City in 2002, has repeatedly said he is desperate to add the Four Hills trophy to his already impressive collection, which includes a world championship gold and a World Cup title.
But he was unable to keep up with his Austrian rivals in the final leg, despite sitting out Sunday's training and qualification rounds to recuperate, and must be satisfied with a tournament third place.
Diethart, in his second World Cup win, now walks home with 20,000 Swiss francs (16,245 euros, $22,121) in prize money and the "golden eagle" trophy.
World champion Kamil Stoch of Poland, the current overall World Cup leader, finished seventh in the Four Hills, having performed poorly at the start of the tournament due to illness.
Japan's Noriaki Kasai, one of the veterans here and a crowd favourite, was fifth in the final standings in his 23rd Four Hills competition.
Austrian record World Cup winner Gregor Schlierenzauer, on the other hand, was unable to defend his title, taking eighth place.
Kasai's Japanese colleague and World Cup number 10 Taku Takeuchi did not compete due to illness, after already missing Sunday's training and qualification rounds.
The ski jumpers now move on to the ski flying event -- which take place on a 200-metre (656-foot) hill, rather than ski jumping's usual 130 or 140 metres -- in Tauplitz, Austria on January 11-12.