Victory gave Bencic, 21, her first win over second seed Kvitova, who had breezed past her in straight sets in the third round of the Australian Open last month.
The win was also Bencic's fourth win over a top-10 player this week after getting past Aryna Sabalenka, Simona Halep and Elina Svitolina in the previous rounds.
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"It's unbelievable, it's incredible. I mean, I still cannot believe it," Bencic told reporters after clinching her first title since she won the Canadian Open in Toronto in 2015. "I'm so happy about the consistency that I could back up my wins. After playing a tough match, I could mentally win another one; it's very difficult."
Kvitova continued to struggle with her rhythm, as she had during the course of the tournament, hitting only 53 percent of first serves on target in the opening set and she also produced seven double faults.
"I think I played better in Melbourne," Kvitova said. "I think definitely I served much, much better in Melbourne than here.
"(During the) whole tournament I was fighting with my serve. It wasn't really great, I played a lot from the second serve." Bencic took the first set with a searing backhand volley that got the crowd on their feet, finally winning a set against the world number four in their fourth meeting.
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Kvitova, however, stepped up her game in the second to break Bencic three times and bagged the set with some powerful forehand returns and by coming up to the net. But it was Bencic who won the mental battle in the third set by breaking Kvitova at 1-1 before winning another break point at 4-2 to serve for the match.
Kvitova's return on match point went long, a decision that was reviewed, to give Bencic the win in an hour and 43 minutes.
She is the second Swiss player to win the tournament after Martina Hingis won the inaugural edition in 2001.
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