Jelena Jankovic recovered from losing the first set to defeat Maria Sharapova 4-6 6-3 7-5 in the DFS Classic final.
Jankovic celebrates her first grass-court title
Russian top seed Sharapova and her second-seeded Serbian rival had earlier come through their semi-finals in the rain-hit Birmingham event.
Jankovic beat Italian eighth seed Mara Santangelo 6-1 7-5, while Sharapova defeated Marion Bartoli 7-5 6-0.
The French fifth seed had joined the final-four line-up with a 5-7 6-4 7-5 win over third seed Daniela Hantuchova.
"I came here not really prepared on grass," she said. "I didn't have much time to get a feeling so I came to get as many matches as possible.
"I didn't really expect to win the title and here I am with the trophy. It's unbelievable.
I think a lot of people knew she was going to be a great player because she had potential from when she was young
"Hopefully, I can get another one this week (at Eastbourne) and go even more confident into Wimbledon."
Jankovic, 22, won her fourth WTA Tour title of the year and denied Sharapova a third Birmingham title in four years.
She went into the final with the advantage of having finished her delayed semi-final two hours before her opponent.
There was little to choose between the players in a tight first set in which both produced their best tennis of the week.
They traded early breaks before Sharapova broke again for 4-3 and went on to clinch the set with an inch perfect lob.
Sharapova appeared to lose focus after netting an easy volley that would have given her a 4-2 lead in the second set and was broken again as Jankovic levelled.
The Russian seemed to step up a gear in the decider, racing into a 3-0 lead.
But a careless service game, in which she was broken to love, allowed Jankovic to recover and she then came from 0-40 down for a crucial hold.
The set then went with serve until Sharapova was broken for a sixth time and Jankovic served out for victory.
Sharapova said: "I grew up with Jelena. We practised for a couple of years together. We were always competing in junior tournaments in Florida and we always had battles when we were young.
"Everyone expected great things from her. Success comes later for some and she's taken some time to develop.
"But I think a lot of people knew she was going to be a great player because she had potential from when she was young.
A spectator had to be airlifted to hospital after she was knocked unconscious when a woman and child fell down a staircase in one of the temporary stands.