Pennetta has now captured two Tour titles this season
Tenth seed Flavia Pennetta won the LA Championships on Sunday after beating Samantha Stosur in straight sets.
The 25-year-old Italian, who had knocked out Maria Sharapova in the semi-finals, struggled with her serve but eventually triumphed 6-3 6-4.
She was also aided by eight double faults conceded by her Australian opponent, who had not previously dropped a set on the way to the final.
It was Pennetta's second WTA Tour title of 2009 following her Palermo Open win.
"I was afraid of her serve, but I returned unbelievably and I think that was the most important thing, " said Pennetta, who was runner-up in Los Angeles last year.
"I've never won a tournament of this size and I'm really happy."
Stosur, who was seeded 13th, is still searching for her maiden Tour title.
"I would have loved to win my first title today, but it wasn't meant to be," she stated.
"I played a very good player today and she played a little better than me."