Red Bull's Max Verstappen won the Austrian Grand Prix for the second year in a row on Sunday, subject to a stewards' investigation, while champions Mercedes lost for the first time this season.
Ferrari's Charles Leclerc, starting on pole, finished second after defending hard against Verstappen with the two 21-year-olds banging wheels as the Dutchman forced his way past. Verstappen took the flag under investigation.
Both 21, the pair were the youngest top two finishers in Formula One history.
Verstappen took the chequered flag, at a scenic circuit owned by Red Bull and with thousands of orange-shirted Dutch fans cheering him on, but still faces an anxious wait for confirmation.
Valtteri Bottas finished third for Mercedes with championship-leading team mate Lewis Hamilton, winner of the previous four races, fifth and behind Ferrari's Sebastian Vettel.
Five-times world champion Hamilton remains well in front in the standings, 31 clear of Finland's Bottas after nine of 21 races.
The victory was the first for a Honda-powered car since Britain's Jenson Button won in Hungary in 2006 for the Japanese manufacturer's own team, and a welcome antidote to last weekend's dull French Grand Prix.
It also ended Mercedes's run of 10 wins in a row, and eight this season.
"For Honda to win again here is incredible," said Verstappen.
"It's hard racing, otherwise we have to stay at home. If those things are not allowed in racing, then what's the point of being in Formula One," he added when asked about the summons to the stewards for the overtake on Leclerc.
The Monegasque, forced wide, said he would let the stewards decide.
"For me it was clear I was on the outside, he left a car width, we touched and I went wide and it's a shame," he said after losing out on his first win for the second time this season.