In a major test for the complicated scoring system now used to judge figure skaters, Lysacek defeated defending champion Evgeni Plushenko of Russia to become the first American winner of the event in 22 years.
Plushenko had a mere .55 of a point lead over Lysacek going into the free skating program Thursday, which meant the slightest bobble on the part of either skater would cost them the title.
Mistakes by both could have handed the gold medal to Japan's Daisuke Takahashi, who eventually finished third.
Both Lysacek and Plushenko turned in dazzling performances, displaying the kind of entertaining skills that help bring figure skating such high television ratings.
When it was over, however, someone had to win and it turned out to be Lysacek -- even though he did not attempt a quadruple jump during his program and Plushenko landed one at the very start of his routine.
Lysacek did land eight triple jumps, four of them in combination with other jumps, and the judges consistently gave him a higher "grade of execution" for the various elements of his program.
His final total for the free skating routine was 167.37 and when added to his short program score he had 257.67 total points.
Plushenko was awarded 165.51 for his program for a total of 256.36. He came out of retirement in a bid to win a second straight Olympic gold medal. Plushenko also won the silver medal eight years ago in Salt Lake City.
No male skater has repeated as Olympic champion since Dick Button in 1948-52.