Red Bull's Max Verstappen took a sensational maiden victory as Mercedes drivers Lewis Hamilton and Nico Rosberg crashed out of the Spanish Grand Prix.
Hamilton and Rosberg came together on lap one as the world champion tried to pass his team-mate, leaving Red Bull and Ferrari to dispute the race.
Verstappen held off Ferrari's Kimi Raikkonen after team-mate Daniel Ricciardo took a three-stop strategy.
Verstappen made his two-stop work to become the youngest winner in history.
Oh dear: replays show it was hard to deifier who was to blame
It was a stunning end to a remarkable race, which started with the unthinkable.
Hamilton, who had taken a stunning pole position on Saturday, made a decent start but Rosberg's was very slightly better and the German was able to draft him down the straight and and pass around the outside into Turn One.
A determined Hamilton was much faster through the fast Turn Three and was closing quickly.
Hamilton dived for the inside on the exit of the corner as Rosberg came right across the track to defend his position. Hamilton did not lift, went onto the grass and lost control, collecting Rosberg's car as he spun back on to the track and taking both out.
The two are to meet the race stewards at 15:30 BST to discuss whether either was to blame and the officials will be taking close note of TV images to see whether Rosberg transgressed the rule that requires drivers to leave space for another car if any part of it is alongside any part of the one in front.
Hamilton's stricken car is loaded onto a truck by stewards
Mercedes non-executive chairman Niki Lauda called the incident "stupid" and blamed Hamilton for being "too aggressive".
But Mercedes F1 boss Toto Wolff said: "It is a very difficult situation, a very difficult incident to analyse.
"It is definitely not clear-cut so I wouldn't want to blame any of them at that stage.
"Lewis had much more speed, Nico closed the door, Lewis was too wide on the inside and lost the car. It is definitely not a 100% pro one and zero the other."
Whatever the results of the stewards enquiry, the incident plays into Rosberg's hands. He retains a 43-point lead over Hamilton but the Briton now has one less race - 16 - to close it down.
Verstappen - only 18 - had Raikkonen within a second of him for the last 22 laps but did not put a wheel wrong to take his first win on his debut for Red Bull, following his promotion from junior team Toro Rosso ahead of this race.
But Ricciardo may feel hard done by after he led the first 28 laps of the race from Verstappen only for Red Bull to pull him on lap 38 and put him on a three-stop strategy, which was calculated to be the slower one before the race.
That put Verstappen into the lead and demoted Ricciardo to third behind Verstappen and Raikkonen.
That became fourth within a few laps because Ferrari followed suit with Sebastian Vettel on the next lap and then made the German's final stop before Red Bull to get him ahead of Ricciardo.
Ricciardo made his final stop on lap 43 - six laps after Vettel - and caught him with 10 laps to go.
Ricciardo made an aggressive but ultimately fruitless dive down the inside of Turn One on lap 59 with seven laps to go.
The move incurred Vettel's wrath as he had to take avoiding action before Ricciardo slid wide and off the track, allowing Vettel to edge back ahead.
"If I don't avoid him he goes straight into my car," Vettel screamed over the radio. "What are we doing, racing or ping-pong?"
Ricciardo kept trying, but Vettel was able to hold him off until with two laps to go Ricciardo suddenly lost pace with a left rear puncture and dropped back.
But he had enough time to make a pit stop for fresh tyres and retain fourth ahead of Williams' Valtteri Bottas.