Granada only dropped four shots over the 72 hole tournament
FINAL LEADERBOARD:-4 J Granada (Par)-2 L Ochoa (Mex)-1 K Webb (Aut)Par I M Chung (Kor)N Gulbis (USA)M H Kim (Kor)A Miyazato (Jpn)+3 P Creamer (USA)
Rookie Julieta Granada held her nerve to win the season-ending ADT Championship by two shots in West Palm Beach, Florida, on Sunday.
Two days after her 20th birthday, the Paraguayan carded a four-under-par 68 to earn the US$1m top prize, the richest ever in LPGA Tour history.
Mexican Lorena Ochoa, who closed to within one shot with two holes to play, ended with a 70 for second place.
Australia's Karrie Webb was third, one shot back on one under par.
The unique $1.5m event featured a starting field of 32 that was trimmed to 16 after Friday and halved again after 54 holes.
In the new play-off format the final eight players faced an 18-hole shoot-out for the bumper prize.
And Granada became the first golfer to make the Tour Championship her first tour title and jumped from 19th to fourth place on the final money list.
This has been one of the most nervous days ever, but now I can look forward to a brilliant off-season
Julieta Granada
"I can't believe I've won $1m in one day," Granada said.
"This is just the perfect way to end a great first year for me on tour."
Ochoa's $100,000 haul was enough to clinch the season money crown with $2.592m dollars because her main rival, Webb, captured only $20,000 for $2.08m.
Japan's Ai Miyazato, South Koreans Il Mi Chung and Mi Hyun Kim, and American Natalie Gulbis finished at level par 72.
American Paula Creamer was last on 75, while Sweden's world number one Annika Sorenstam missed the cut on Saturday.
Granada, whose previous best finish was second at the Wegmans Rochester International in June, is the first player from Paraguay to win an LPGA tournament.
She moved clear with a third birdie of the day at the 10th and three ahead when she made another at the 16th.
But Ochoa, playing with Webb at the back of the field, mounted the pressure and closed the gap to one shot with birdies at the 15th and 16th.
However, a missed green and a bogey at the 17th virtually ended her hopes of a seventh win of a superb season.
Granada added: "I knew Lorena and Karrie were closing the gap and this has been one of the most nervous days ever, but now I can look forward to a brilliant off-season."