The 28-year-old Clay completed the 10-discipline event with 8,791 points to beat Andrey Krauchanka of Belarus and Cuba's Leonel Suarez by a wide margin. Krauchanka and Suarez took the silver and bronze 8551 and 8527 points, respectively.
A triumphant moment for Bryan Clay, who failed to win in Athens four years ago. "I can't tell you how happy I am to have completed something I have been working on for so long. It's a dream come true," said Clay, who hopes to become the first decathlete to win three Olympic medals in London in four years time. "It's the start of something good and if my body holds up I'm hoping to be capable of doing this again in 2012."