Fill clocked 1min 52.37sec down the notoriously difficult Streif course, slightly shortened because of high winds and heavy early morning snowfall.
Swiss pair Beat Feuz and Carlo Janka rounded out the podium at 0.37 and 0.65sec respectively.
“I feel great, it's a great day for me, a real dream come true,” said Fill. “This is the biggest race of the season given there's no Olympics or world championships.
“I had one goal this year and that was to go fast in either Wengen or Kitzbühel. Wengen was not so good for me so I'm happy to win here.”
Norway's Svindal and Austrians Hannes Reichelt and Georg Streitberger all crashed out in dramatic fashion in the same Hausberg Kompression turn, within view of an estimated 50,000 spectators packed into the picturesque Tyrolean town.
Coming out of the Hausberkante, the course demands everything of man and material as racers fight not only creeping exhaustion but also a 3.5G centrifugal force to change direction into the final descent.
Streitberger, a three-time podium finisher in Kitzbühel, crashed first. No sooner had the helicopter parked than it was up in the air again, this time to scoop up 2014 winner Reichelt.
– 'Insane crash' –
Svindal was next, and although the in-form Norwegian, on a streak of seven victories this season, was at least able to walk away from his horrific crash in very tricky conditions including a rough track and limited visibility amid sporadic snow flurries, he was later ruled out for the season.
“Aksel ruptured the anterior cruciate ligament of his right knee. He's in the process of being operated on. His season's over,” Norwegian ski federation official Claus Ryste told NRK.
The crash brought an immediate reaction from American speed queen Lindsey Vonn, a racer who knows all about season-ending crashes but who was talking after just setting a record for most women's downhill wins after another victory in Cortina.
“Oh my dear lord that was an insane crash!! That's a miracle @akselsvindal is walking away from that!!!” she tweeted.
Reichelt complained of a headache but it was also not good news for Streitberger, who tore knee ligaments to add to a mounting injury list on the Austrian speed team.
Fill admitted that it was “never nice to see other racers crash”.
“When you start here, you know it's really dangerous and you know you need to risk a lot and hope you come down in one piece,” the Italian said.
Each time there was a fall, gasps went up from the crowd that included the likes of former California governor and Hollywood star Arnold Scwarzenegger and ex-Formula One driver Nikki Lauda, followed by a deathly minutes-long silence.
Fill picked a steady line down, starting with bib number 14 and hitting speeds in excess of 120km/h, for just his second victory on the World Cup circuit at the age of 33.
Last year's winner, Kjetil Jansrud of Norway, finished 14th, 1.89sec off the pace, as Norwegian hopes of extending their remarkable winning sequence of 13 victories from 22 races this season came to an abrupt halt.
Organisers took the decision to end the race after 30 runners, meaning 27 competitors missed out on racing what is regarded as the Superbowl of the sport: the Hahnenkamm, or rooster's comb, the mountain on which the “Streif” piste lies, widely recognised as the toughest course on the demanding World Cup circuit.
Overall World Cup leader Svindal won Friday's super-G, but second-placed Austrian rival Marcel Hirscher has the opportunity to claw back some points and even leapfrog the Norwegian in Sunday's slalom, with the two legs scheduled for 0930 and 1230 GMT.
Alexis Pinturault led a French podium cleansweep of Friday's combined event, teammates Victor Muffat-Jeandet and Thomas Mermillod Blondin finishing second and third for a first Tricolor 1-2-3 since 1970.