Joint winner of the Bormio classic earlier this season, the 23-year-old Paris outshone the favourites in one minute 57.56 seconds to emulate compatriot Kristian Ghedina, crowned in 1998.
"Who wouldn't dream of winning Kitzbuehel? " said the skier from Merano, in the South Tyrol.
"To win Kitzbuehel is a career high, something very special for a downhiller, I didn't feel so good up there but I nailed the final part really well. It's the kind of course I like the most, you have to fight from top to bottom, like at Bormio."
Paris fended off questions about his chances at the world championships in Schladming which start on Feb. 5.
"I don't want to think about Schladming. Kitzbuehel is Kitzbuehel. Nothing else matters for now," he said.
The victory underlined the strength of the Italian speed team, who have bagged four of the six downhills held this season, with Christof Innerhofer winning in Beaver Creek and in Wengen a week ago.
Innerhofer was the focus of attention for the 50,000 spectators lining the Streif on Saturday, as he started in 46th position after being sanctioned for ignoring an order to slow down in practice.
Threatened with losing his racing licence after criticising the International Ski Federation (FIS) on Austrian television, Innerhofer was allowed to race with a fine and a high start number after he apologised.
As visibility worsened, the super-G world champion finished 21st, 1.92 off the pace.
Erik Guay was second, 0.13 seconds adrift, the best result for a Canadian on the Streif piste in 30 years.
"A podium finish in Kitzbuehel is amazing, something I have been aiming for for a long time," Guay said. "It is for sure a special place for the Canadians and it means a lot to do so well in the last speed race before the worlds."
Hannes Reichelt, who shared victory with Paris in Bormio, salvaged Austrian pride by finishing third, 0.36 behind the winner.
Aksel Lund Svindal, the fastest in practice and winner of Friday's super-G, looked a clear favourite at the start but could manage only 10th place, 1.16 back.
Perhaps unsettled by the crash of Frenchman Johan Clarey, who started ahead of him, the Norwegian surrendered the downhill World Cup lead to Paris by six points while losing vital ground in the race for the overall title to Austria's Marcel Hirscher.
Hirscher will be the favourite at home in Sunday's slalom.
The demanding course claimed its usual share of victims, most spectacularly Peter Fill, who somehow walked away after clipping a barrier and being flung through the air.
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