Australian veteran Mathew Hayman beat four-time winner Tom Boonen in a dramatic finish to win the Paris-Roubaix one-day classic.
The 37-year-old edged out the Belgian by a bike length as Britain's Ian Stannard finished third.
"I broke my arm five weeks ago and missed all the racing," said Hayman. "I raced a race in Spain last week.
"This is my favourite race. It's a race I dream of every year. This year I didn't even dare to dream."
Orica Greenedge rider Hayman was riding in his 15th Paris-Roubaix and is the second Australian to win the race after Stuart O'Grady in 2007.
Pre-race favourites Peter Sagan and Fabian Cancellara were both caught out by crashes and finished well back.
The 257.5km route across northern France, nicknamed the 'Hell of the North', is famous for its cobbled sections.
Team Sky rider Elia Viviani, 27, was taken to Valenciennes hospital after being involved in a crash with a motorbike during the race.
Video footage shows the motorbike crashing into barriers and Viviani before the Italian walks away from his bike clutching his chest.
"He thought he'd anticipated the crash and saw it happen in front of him. He managed to come to a stop on the right by the barrier when the motorbike went into him," said Sky's team doctor Derick Macleod.
"He's got a few bruises and abrasions and he's a bit sore obviously, but we're really thankful he's got no significant injuries."
1. Mathew Hayman (Aus/Orica) 5:51:53
2. Tom Boonen (Bel/Etixx - Quick-Step) Same time
3. Ian Stannard (GB/Team Sky) Same time
4. Sep Vanmarcke (Bel/LottoNL) Same time
5. Edvald Boasson Hagen (Nor/Dimension Data) +3 secs
6. Heinrich Haussler (Aus/IAM Cycling) +1 minute
7. Marcel Sieberg (Ger/Lotto) Same time
8. Aleksejs Saramotins (Lat/IAM Cycling) Same time
9. Imanol Erviti (Spa/Movistar) + 1:07 mins
10. Adrien Petit (Fra/Direct Energie) +2:20 mins