Wayde Van Niekerk said he always believed he could break Michael Johnson's 400 metre world record after winning gold in remarkable fashion at the Rio Olympics.
The South African upstaged Kirani James and LaShawn Merritt with a sensational time of 43.03 seconds on Sunday.
Van Niekerk left his rivals well behind, beating the mark set by Johnson (43.18secs) at the 1999 World Championships.
"I believed I could get the world record," said Van Niekerk, who was congratulated by 100m champion Usain Bolt after the Jamaican won yet another gold.
"I've dreamed of this medal since forever. I am blessed."
The previous two champions, James in London and Merritt in Beijing, were the pre-race favourites.
Grenadian James, who had to settle for a distant second despite running faster than he had en route to gold four years ago, said he was simply pleased to be part of a historic race after winning silver ahead of the American.
"I'm happy to be part of a race that made history," James stated. "We have put this sport on a pedestal."