PARIS, JUNE 9 -- Monica Seles, a girl with killing strokes and a cartoon laugh, became the youngest female champion in French Open history today. The 16-year-old from Yugoslavia didn't just upset No. 1-ranked Steffi Graf of West Germany, she knifed her in straight sets, 7-6 (8-6), 6-4, and then disarmingly laid her cheek against the silver trophy.

Graf, the most dominant player of her generation, was driven from one end of Stade Roland Garros to the other, and into the depths of uncertainty by this slight, unorthodox player who swings at the ball with both arms -- backhand and forehand. The 20-year-old 1988 Grand Slam winner lost the first set despite holding leads of 5-0 and 6-2 in the tiebreaker. No. 3-ranked Seles, urged on by roars and the thought of the Lamborghini sports car she intends to ask her parents for, flailed her way out of four set points and swept the last six points of that tiebreaker.

After an array of searing winners and a gift of a double fault from Graf, she swung her fist in an uppercut and jerked her knee into the air with elation. It was where the match turned, Graf never leading again. Seles fought off two late, crucial break points in the second set to hold her serve and then broke Graf a shocking fifth time to ensure the straight-set victory.

"I really didn't think I could do this," said Seles, who is a U.S. resident living in Bradenton, Fla., with her parents. "I didn't expect to have such a great couple of weeks of my life."

Graf has been an unassailable No. 1 for three years, but she was tremulous and casting about in the aftermath of such a defeat, the second straight time she was upset in the French by an adolescent. Seles surpassed last season's darling, Arantxa Sanchez Vicario, then 17, as the youngest French victor.

"I think I'm lacking a little confidence right now," Graf said. "I'm not hitting the ball like I used to, I'm making more mistakes. Something is missing."

Graf had won eight of the previous nine Grand Slam events, the Australian, French and U.S. opens and Wimbledon. But this may be the start of a fascinating new era. Just three weeks ago, Seles beat Graf soundly at the German Open in West Berlin, 6-4, 6-3. That broke Graf's winning streak of 66 matches -- the second longest in history to Martina Navratilova's 74 -- and perhaps the spell of fear she has held over the women's game.

Now it is Seles who is on an astounding run. This was her sixth consecutive tournament title and 32nd successive match victory, including a straight-set defeat of No. 2 Navratilova in the Italian Open final. Today she claimed the one thing she lacked, a major championship, becoming the second-youngest winner of a Grand Slam event behind Charlotte "Lottie" Dodd of Britain, who in 1887 won Wimbledon at 15 years 10 months.

"She's not a nightmare yet," Graf said. "I hope she's not becoming one."

But Graf clearly is unnerved. The left-handed Yugoslavian has awkward, deceptive strokes that find odd angles and paths up the lines. She also has grit, three times nearly upset earlier in the tournament but somehow surviving.

Seles rallied from a set down to defeat Helen Kelesi in the second round, needed two tiebreaker sets against Leila Meskhi in the third round, and was two points from defeat before ousting sixth-seeded Manuela Maleeva in the quarterfinals.

A drawback to Graf's coiled whip of a swing is that she is late in starting her windup. Seles' hard, low ropes made Graf pay for that, catching her before she was ready and causing sprayed errors, 35 in all.

Seles also has at least as much pace as the West German and is a brilliant returner of serve. Graf was not used to having her once unequaled force thrown back at her; usually she rakes opponents with aces and winners until they are intimidated. But Seles fearlessly slammed almost as many winners in return, 25 to Graf's 28. It made a compelling duel as they lashed out from the baseline.

"I just really wanted to enjoy this match," Seles said. "I wanted to make her play. I wasn't afraid."

The first point of the match was a harbinger, as Seles drove a huge forehand return straight down the line for a winner. But there is no safe margin against Graf, who surged back. As Graf served to take her first lead in the 11th game, 6-5, they played their most spectacular point, every shot a heart-stopping near winner. Seles was stretched way off the court by a forehand but flicked back a reply and retrieved a drop shot before Graf ended the rally with a another sliced forehand drop shot that landed like a stone.

In the tiebreaker, Seles suddenly lapsed while Graf carved out her 5-0 lead. When Seles rushed a forehand into the net, Graf had quadruple set point, 6-2.

"I was sure I was going to win it," Graf said.

But Seles awoke with a cracked, backhand return winner that ticked the line, a big service winner and an overhead set up by another backhand for 6-5. Then Graf double-faulted to make it 6-6, her set points gone.

"I played them very badly," Graf said. "You have four set points, you have to go for at least one of them. If I had won the first set I would have won the match. But I didn't."

Seles delivered a twisting serve to Graf's backhand, and the reply sailed deep to give the Yugoslavian set point. In what was the pivotal moment of the match, Seles seized it with a savage forehand passing shot up the line that Graf could only dive at.

"If you had told me before I wouldn't have believed it," Seles said. "I thought if she had me 5-0, maybe I could make it 5-5. . . . When it was 6-6, I knew I had her."

Graf was hesitant throughout the second set. She trailed by 3-0, recovered, then lost her last opportunity to extend the match when she got two break points on Seles' serve in the ninth game, but couldn't execute. Seles killed the first with a driving backhand, the second with a slashed forehand down the line.

Seles then broke a final time to close the match. She jammed a short backhand down the line for double match point, and Graf floated a listless forehand deep on the first ball to end it quickly. It was an uncharacteristic finish by the usually ruthless Graf, a sign of nagging uncertainty.

"It started in Berlin and it took over a little bit here," Graf said. "It's difficult to get it back somehow. Today was so close, and I just didn't do the right points and right shots. That's usually something very strong about me."

An illustration of that was the fact that Graf had nine opportunities to break Seles' serve. Seles, with just six chances to break Graf, summoned a big shot five times.

Seles later said she felt her hard work entitled her to a sports car.

"The car I want will take a lot of convincing of my parents because it is too fast," said Seles, with a staccato Woody Woodpecker-like giggle. " . . . This is probably the best time to convince them."

Graf always has borne her fame and success uneasily, and is enduring a particularly difficult season on and off the court. Self-doubt may have sprung up when she played poorly in capturing the Australian Open in January. She suffered a freak cross-country skiing accident, breaking her thumb while fleeing paparazzi in Switzerland; she missed almost two months of play. Unpleasant stories about her family have appeared recently in German and British tabloids. She was plagued by allergies throughout this tournament.

Graf struggled to explain the loss, no longer a rising prodigy like Seles but a chased and pressured champion who now knows the trials of the spotlight and having to constantly defend, while all the carefree little Seleses harry her.

"She's risking, she goes for it, and she's not missing," Graf said. "She has a freshness."

SELES (2) def. GRAF (1)

7-6 (8-6), 6-4

.....................Graf.....Seles SERVES

Aces...................2......0

Winners................3......0

Double faults..........1......1

1st-serve percent.....72.....74

1st-serve pts. won...30-51...29-56

2nd-serve pts. won....8-20...12-20

RETURNS

In-play percent......89......89

Break points.........14...... 9

Break pts. converted..4...... 5

Conversion pct.......44......83 NET PLAY

Points won..........13-21....3-5

Winners at net....... 4...... 2

Forced errors at net..0...... 0

Unforced errors at net.2......1

Times passed...........4......1 BASELINE

Forehand winners......17......7

Backhand winners.......2.....16

Forehand forced errors.8......8

Backhand forced errors.6......8

Fore. unforced errors..18......12

Back. unforced errors..14......15 SUMMARY

Winners................28......25

Forced errors by.......14......16

Unforced errors by.....35......29

Points won...........73-147..74-147