Russia's Andrey Moiseev stormed to victory in the 3,000m run to comfortably secure the men's modern pentathlon gold medal on Thursday.
Moiseev, who had already won in the fencing and swimming, made the most of his 11-second lead to ease past the finish line first in the final event.
Lithuania Andrejus Zadneprovskis made a late surge to land the silver, while Czech Libor Capalini took bronze.
Moiseev, 25, clocked 1:58.88 in the swim to set an Olympic record.
His final score was 5480, with world champion Zadneprovskis behind on 5428 and Capalini on 5392 in the competition which involves shooting, fencing, swimming, showjumping (complete with hunting jacket) and a 3,000m run.
"It hasn't quite sunk in yet," said Moiseev, who is ranked 10th in the world but only won an individual World Cup event for the first time this year.
"I had enormous faith in myself. I went for it from the first metres of the run."
Capalini was astonished to win bronze after finishing 13th in the opening shooting discipline and 19th in fencing.
"To make so many mistakes and still come away with a medal - I didn't expect that," the Czech said.
Moiseev established his lead after devastating the field in the swimming discipline, which he completed more than three seconds ahead of his nearest challenger.
He also won the fencing discipline, dragging himself up to second from 19th place he had occupied after the opening event, shooting.
Moiseev had six gates down in the unpredictable showjumping event to cut his lead to just 44 points - or an 11-second headstart in the final cross-country run.
But it was more than enough as the jubilant Russian jogged over the finish line, draped in the Russian flag, to claim the gold medal.