The Briton had already won in Moscow in 1980 against a field shorn of several top competitors by boycotts, but in L.A. he faced his long-time rival Juergen Hingsen of West Germany.
Thompson came into the games boasting a six-year winning streak, and was in no mood to relinquish it.
He famously trained on Christmas day to gain an edge, and Sebastian Coe once said of Thompson: "Daley is a Stalinist. It's not enough to win; he has to mentally destroy his opponent."
A formidable sprinter and jumper, Thompson jumped into an early lead on day one, which featured his best events, and never looked like letting go.
Thompson won by over 100 points, and equalled Hingsen's world record of 8,798 points, though he would have taken it outright had he not eased off in the 1500m.
Never the most diplomatic, Thompson chose to celebrate his victory with a t-shirt asking: "Is the world's 2nd greatest athlete gay?" - a reference to Carl Lewis - before suggesting that Princess Anne might like to have his babies. She didn't.