Maze was involved in the first Alpine skiing tie at the Olympics in the downhill, clocking exactly the same time as Swiss Dominique Gisin, and she was only 0.07 seconds away from a repeat despite building a half-second lead in the first run.
Germany's Viktoria Rebensburg, giant slalom champion in Vancouver four years ago, produced a superb second run through driving snow and fog to snatch the bronze behind Fenninger, who won the super-G gold at the weekend.
After disappointment in the opening super combined race at Rosa Khutor, when she missed a medal, all-rounder Maze has gone from strength to strength.
"I feel really wet but I feel great to win my second gold," Maze, who won last season's overall World Cup with a record-breaking points total, told reporters as the rain poured down.
"It's what I came here to do. I'm very proud and I think I will realise what I've done years later. Right now it's just go with the flow and not get too emotional.
"We had two weeks of sun here and I knew it couldn't last...but it can rain as much as it wants."
Having carved out a 0.52-second advantage in the first run Maze was clear favourite for victory when the second run began after a short delay due to a snowstorm at the top of the hill.
American teenager Mikaela Shiffrin, fifth after the first leg, briefly looked in contention for a medal on her Olympic debut but ended up in that same fifth spot.
Rebensburg's second attempt through the 54 gates elevated her to third, 0.10 seconds behind Fenninger, who was delighted with a silver to add to her super-G gold.
"I just can't believe that I got a second medal, it's so cool and I'm so stoked about my second run," Fenninger said.
"If someone said I would get two medals I would have said that's nice but it's too hard."
Former Olympic giant slalom champion Julia Mancuso of the United States missed a gate in her first run while another medal contender, Germany's Maria Hoefl-Riesch, did not start.
Violin virtuoso Vanessa Mae provided a cameo performance as she made her Olympic bow skiing for Thailand.
She managed to complete both runs at rather "waltz-like" pace, 50 seconds slower than the winner in 67th and last place.s