For the first time in the history of the World Cup, the overall title was decided on the very last run of the last race of the season.
Fenninger had been fastest in the first leg of the closing giant slalom and handled the pressure, winning with a 0.38 seconds lead over team-mate Eva-Maria Brem.
Slovenia's Tina Maze, the 2013 overall champion who had led Fenninger by 18 points in the standings before the race, finished third and 0.46 seconds short of her second World Cup title.
Maze ultimately lost out by 22 points.
"I had to find some extra strength to win this race and everything that went along with it. It’s over at last and the pressure eases off. I don’t really know what to think just yet,” Fenninger said.
"I had so much pressure. I’m glad things worked out well again but I’m as much tired as I’m happy. I can imagine how disappointed Tina must be but in a few days she’ll realise what a great battle that was.
"For me, it was the craziest experience I ever had."
The men’s World Cup showdown was also a tight one but the outcome was the same as last year with Austria's Marcel Hirscher bagging his fourth big globe in succession.
Maze, who led the way for most of the season, ended the winter with the consolation of the downhill and super-combined world championship golds while Fenninger took the giant slalom and Super-G in Beaver Creek a month ago.
Lindsey Vonn, the other star of 2014-2015 who bagged the downhill and Super-G crystal globes, finished off with a promising fifth place in Sunday’s giant slalom.
It was also a season of farewells as Swiss downhill Olympic champion Dominique Gisin announced her retirement along with Spain’s Carolina Ruiz-Castillo and Frenchwomen Marion Rolland and Marie Jay-Marchand-Arvier.
(Writing by Francois Thomazeau, editing by Alan Baldwin)
