Rolland, remembered for a freak crash at the 2010 Vancouver Games when her knee snapped seconds into the Olympic downhill, won by 0.16 seconds from Italy's Nadia Fanchini with a time of one minute 50.00. German Maria Hoefl-Riesch took bronze.
Rolland can claim to be the first Frenchwoman to win the most prestigious world title, though her compatriot Marielle Goitschel is widely considered as the winner of the 1966 downhill world crown after a gender test the following year showed that the champion on the day, Erika Schinegger, was actually a man. The Austrian was never officially disqualified.
"I wanted a medal here at all costs," Rolland, 30, said. "I gave it my all because I believed in my chances.
"I had good feelings on this piste, which I liked very much since last season," she said.
Rolland has never won a World Cup event but earned her first two podiums last season on Schladming's Streicher piste, finishing second in the downhill behind Lindsey Vonn.
In the absence of the American Olympic champion, who was injured in the opening event of these championships, the downhill race was wide open.
"To win gold is obviously incredible, I dreamt about it like every young athlete. You have to believe in your dreams and your goals and fight hard to reach them," added Rolland, whose grandfather Antonin won two stages of cycling's Tour de France in the 1950s.
Fanchini, who like Rolland has had a career hampered by serious crashes and injuries, took advantage of her early start number to get on to the podium.
"I tried to ski the way I did before my serious crash in St Moritz in 2010," said the Italian, whose sister Elena was also downhill silver medallist at the Bormio worlds in 2005.
The course, unusually icy for a women's race, was too hard to handle for most skiers and several spectacular crashes caused long delays.
As a result, snow and visibility conditions changed in the middle section, making the course slower for the later starters and Rolland's performance, with bib number 22, all the more impressive.
Hoefl-Riesch was the only favourite to live up to her reputation, adding a bronze medal to her super-combined gold from two days ago.
"I'm glad to be on the podium of a very tricky race because of the changing light from one section of the course to the other," the German said.
"It's a podium for the war-wounded as we have all had serious knee injuries in our careers."
Pre-race favourite Tina Maze of Slovenia, who had been bidding to win medals in all five events in Schladming, had to settle for seventh place, 1.21 adrift.
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- Nadia Fanchini