BEIJING Usain Bolt, the Jamaican sprinter who has crashed the international sprint scene this year, obliterated his own world record by winning the gold medal in the 100 meters in theatrical fashion Saturday night at the Beijing Olympics.

Starting in Lane 4, Bolt had an average start but blew away the field in the final 50 meters, spreading his arms with three strides to go and pounding his chest before crossing the line in 9.69 seconds. If he had held his form through the tape, he might have run under 9.6.

Richard Thompson, the N.C.A.A. champion from Louisiana State who competes for Trinidad and Tobago, finished second in 9.89 seconds. The American Walter Dix, who competed at Florida State, won bronze in 9.91.

Next for Bolt is the 200 meters, in which he will be even more of a prohibitive favorite. Carl Lewis was the last sprinter to win both the 100 and 200 in the same Games, at the 1984 Los Angeles Olympics.

Bolt had run the most impressive preliminary rounds and seemed the most relaxed and confident among the sprinters before the race, dancing around near the starting blocks.

With a body seemingly ill-suited for the blink-and-its-over 100-meter dash, the 6-foot-5 Bolt won track and fields marquee event in front of more than 90,000 fans at the Birds Nest, just 10 weeks removed from his breakthrough performance in New York City. On May 31, competing in the Reebok Grand Prix on Randalls Island, Bolt ran a 9.72, breaking Asafa Powells record of 9.74. Powell, also from Jamaica, was fifth Saturday night, in 9.95.

The mens 100 final was missing one of the top contenders, the American record holder and defending world champion Tyson Gay. He failed to advance out of his semifinal heat Saturday night, finishing fifth in 10.05 seconds and stealing the final of some of its anticipated luster. Gay finished behind Powell, Richard Thompson and Darvis Patton in the semifinal heat. Gays only chance at Olympic medals will be in the relays.

I dont really have any excuses, I just didnt make it, Gay said. My hamstring felt good. It didnt bother me. I wasnt too overwhelmed with this being the Olympics. Maybe I could have used some more training or more races but besides that, I was just trying to get my rhythm through each round.

Powell, 25, who held the world record from June 2005 until May, won his semifinal heat in 9.91. Bolt, 21, ran a 9.85 seconds despite slowing toward the end.

Bolts height makes him somewhat of an unlikely success in the 100, a burst that typically favors shorter, stockier runners. But he manages to reach blazing speed with unusual stride length and stride frequency.

The meet in New York in May was only the fifth time Bolt had run the 100 professionally, but he could boast two of the three fastest times ever. Although he was not yet an international star before 2008, Bolt has long been highly regarded in the track community. He won the world junior championship at 200 meters at age 15. He later was the first junior sprinter to break 20 seconds for the 200.