The Briton deposed her friend and training partner Maria Mutola as women's 800 metres Olympic champion in one of the biggest Athens upsets.
Holmes, who had never won a major title before and whose career has been blighted by serious injury, timed one minute 56.38 to win a blanket sprint to the line on Monday, following a brilliant tactical display.
Mutola, the dominant force of the event for around a decade and who had helped to breathe new life into Holmes's career, went away empty-handed.
"I can't believe it. I didn't realise I had won," the said the 34-year-old Holmes, who won bronze in Sydney. "I'm in shock -- absolute shock.
"I knew I was in front but had to see the replay twice to make sure. I was just digging in."
The British runner had enjoyed the worst of luck before today's shock.
She had only six weeks' training after injury before the 2000 Olympics and ran with a stress fracture in the 1996 Games. She was favourite for the 1997 worlds but ruptured her Achilles tendon and tore a calf muscle just before the competition.
For persevering when the going got tough in the manner of true champions, Kelly Holmes is our deserving Olympian of the day.