Kvitova saw off Australia's Ashleigh Barty 4-6 6-3 6-2 in Birmingham in only her second tournament since the start of her comeback at the French Open last month.
The two-time Wimbledon winner was stabbed in the Czech Republic in December and could have lost her career, escaping instead with hand injuries.
But in a stunning performance against Barty, Kvitova battled back from losing the first set and stepped up in the second half of the decider to seal victory.
She said: "I'm very, very happy, of course. I didn't expect this in my second tournament after my comeback. So yeah, I think it's kind of a fairytale.
"I think I've been through a very difficult time in my life, and it wasn't about the tennis, but about coming back healthy and alive and move my fingers properly and everything like that. And this is something clearly special.
"It's some bonus to have my life and my career and everything. And that's why I fight that hard to come back to play tennis.
"And I always said that I'm not here just to play tennis. I'm here to play my best and to win trophies, like today. So I have to say I'm kind of proud of myself that I did it today."
Barty, the world number 77, made a strong start as she broke to lead 2-1 in the opening set and carried her advantage through to claim the opener with relative ease.
But Kvitova stepped up her game at the start of the second, breaking for 2-0 and moving to the brink of levelling the match when she secured a double break to move 5-1 in front.
Serving for the set, the Czech suffered an attack of nerves as two double-faults enabled Barty to claw one break back, but that was not enough as Kvitova served out for the set at the second attempt.
Kvitova seized control of the decider as she broke immediately then pressured the Barty serve again only for the momentum to swing again as the Australian broke back to level at 2-2.
But a fired-up Kvitova responded immediately as she blasted back from 40-0 down to reel off a series of winners and once again take control of the set.
Building on her advantage, Kvitova followed up with a second break before serving out strongly with an ace to seal her remarkable comeback success and despite tasting defeat Barty was full of admiration for her opponent.
"It's so amazing to have Petra back on the court. She's such an inspiration," said the Australian.
"She's always been a great champion but I think we appreciate that more now that she's back playing week in and week out."
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