The Australian finished with 32 unforced errors to on 16 by Pennetta.
“Sure, I’m disappointed,” said the 25-year-old Stosur, who has yet to clinch a title in five finals. “I would have loved to win my first title today, but it wasn’t meant to be.”
The 10th seed knocked off second seed Vera Zvonareva and three-time grand slam champion Maria Sharapova en route to the crown.
Pennetta broke Stosur to win the contest when she exhausted the Australian in a long rally and finally took it with a forehand crosscourt winner.
In the doubles final, Chuang Chia-jung of Taiwan and Yan Zi of China, defeated Maria Kirilenko of Russia and Agnieszka Radwanska of Poland, 6-0, 4-6 (10-7).
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