With her forehand in scintillating form, the fourth-seeded Australian delivered a ruthless display on the green claycourt surface at Daniel Island to win her fifth successive match against the Russian.
World number 11 Stosur, who reached the semi-finals of the elite Indian Wells tournament last month, broke her opponent three times in dazzling sunshine to sweep through the opening set in 18 minutes.
Trailing 0-3 and 15-40 on serve in the second, seventh-seeded Zvonareva won her first game of the match after repeatedly smashing her racket to the ground in frustration.
"To be able to do that through the whole two sets and not really let up was a great feeling," a beaming Stosur said in a television interview after being presented with the tournament's crystal trophy.
"It's always great to be able to play well in any match but to do it in a final where there's lots of pressure and you want to win that extra little bit more is really, really great."
The Australian, wearing a wristband embellished with the words "attitude" and "composure," struck 36 winners against Zvonareva and made just 11 unforced errors.
"Having made the (French Open) semis last year and after this week, I am feeling great on the clay," said Stosur who reached the last four in a grand slam event for the first time at Roland Garros.
"I have played five consistently good matches here so going into Roland Garros I am going to be ready to go and definitely trying to at least repeat last year."
(Writing by Mark Lamport-Stokes in Los Angeles; Editing by Justin Palmer)